Category: Troubleshooting

Cloudy aquarium water has three common causes, and they need different fixes. Milky grey water with no visible particles is a bacterial bloom, which usually clears on its own in a new tank. Cloudiness straight after filling a new soil tank is soil dust. A haze after a water change that has gone by morning is just air.

Which kind do you have?

What you see	Likely cause	What to do
Milky light grey, no particles you can see	Bacterial bloom	Leave a cycling tank alone; find the cause in an established one
Cloudy right after filling a new aqua soil tank	Soil dust	Drain it, refill slowly, filter off until clear
Haze an hour after a water change, gone overnight	Dissolved air coming out as tiny bubbles	Nothing. It’s harmless
Green tint	Free-floating algae (green water)	A different problem

A bacterial bloom

Aquasabi describes water that turns milky within a few days, with its clarity much reduced but no floating particles visible to the naked eye. That last point rules out dust and debris. Aquarium Science compares it to milk poured into the tank.

It is most common in a new tank that is still cycling, according to both sources. In an older tank, Aquasabi points to seasonal heat or extra daylight. Aquarium Science traces it to food and waste releasing dissolved organic compounds that feed bacteria in the water, and ultimately to a filter that can’t keep up. That happens when the filter is less than three months old, has been replaced or scrubbed, has been hit by medication, or when the tank is overfed. It adds that bloom bacteria are rarely pathogenic.

What to do, and where the sources disagree

In a cycling tank, Aquarium Science says to leave it alone: changing water simply prolongs it, and it typically clears within a few weeks as the bacteria move from the water to the filter. If a lot of food has gone in, the advice reverses: get it out fast with several near-complete water changes.

Aquasabi, which sells UV units, recommends running a UV-C clarifier temporarily on a slow, separate pump. It says the water clears within a few days, and that you should then change as much water as possible and not leave the unit running in a planted tank. Aquarium Science agrees UV clears it, often overnight, but calls it a stopgap that leaves the cause in place, and doesn’t recommend it.

Soil dust in a new tank

This one comes from aqua soil, and the source here is ADA writing about its own Amazonia soil. Cloudiness right after the first fill happens when the granules have dried out or crumbled into powder. ADA’s fix is to remove all the cloudy water and pour new water in slowly, repeating as needed, or to fill with one hose while draining with another.

Keep the filter off until the water is clear. ADA warns that running it on cloudy soil water can feed a bacterial bloom or green water from the fine particles. To avoid the problem at set-up, let water trickle from a hose onto the hardscape rather than pouring from a bucket, and plant straight away. Our aquasoil page covers the rest of a soil set-up, and the Walstad method page covers ordinary soil.

If the cloudiness never quite goes, ADA names two causes: a filter outlet stirring up the substrate or an intake set too low, and shrimp pecking at exposed soil. The particles fall away as plants grow over the substrate.

Keeping it clear

Most of the prevention is about the filter. Aquarium Science says not to clean biological filter media more than once every four months to a year, and then only with a light swish in a tub of water, never under the tap, because the brown gunk is the beneficial bacteria. Feed moderately, and keep the water well aerated so the filter bacteria can work.

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Cloudy water questions

How long does a bacterial bloom last?

Left alone in a cycling tank, Aquarium Science says the water typically clears in a few weeks. Aquasabi says a UV-C clarifier clears it within a few days, though Aquarium Science warns that it leaves the cause in place.

Should I do a water change for cloudy water?

It depends on the cause. For a bloom in a cycling tank, Aquarium Science says water changes only prolong it. For soil dust after filling, ADA says to drain the cloudy water. For excess food, change most of the water, several times.

Is cloudy water harmful to fish?

Usually not directly. Aquarium Science says bloom bacteria are rarely pathogenic. The bigger risk in a tank that is still cycling is ammonia, so test it if fish are in the tank.

Sources: Aquasabi, Bacterial bloom; Aquasabi, Algae in the aquarium; Aquasabi, Green water; Aquasabi, UV-C clarifier; ADA, Aqua Soil Amazonia (via Aquasabi); Aquarium Science, Cloudy water.

Aquarium plants turning yellow usually lack a nutrient, and where the yellow appears narrows down which. Aquasabi says to rule out a CO2 shortage first, then look at older leaves for nitrogen, magnesium and potassium and at new growth for iron. New plants dropping the leaves they grew above water is a common false alarm.

Check these first

Not every yellow leaf is a deficiency. Aquarium Science points out that many plants are grown with their leaves in air, and those leaves typically die back once submerged and are replaced by new ones. That is normal in a new tank; our plant melt page covers it. Aquasabi adds that some pure white LEDs make bright greens look pale, which can pass for yellowing.

Then rule out CO2. Aquasabi says most deficiency patterns, yellow leaves included, can also be caused by a carbon shortage, so it should be considered before any other nutrient. Tropica agrees that insufficient CO2 can leave plants stunted or discoloured.

Old leaves or new growth?

Where the yellow starts is the clue. Nutrients a plant can move are drawn into new growth, so their shortage shows in older leaves first. Nutrients it can’t move show in new growth first. The patterns below are Aquasabi’s.

Where	What you see	Likely shortage
Older leaves	Overall yellowing; new leaves come in smaller, some species redden	Nitrogen
Older leaves	Pale or yellow, with the veins staying green	Magnesium
Any leaf	Small black dots that become holes edged in yellow or black	Potassium
New shoots	Tips turning yellow to white, clearest on fast stem plants	Iron
Shoot tips	Very slow growth and shrinking tips, sometimes darker or violet	Phosphorus (not yellowing)

Aquasabi warns that these patterns overlap, so treat a diagnosis as a best guess and change one thing at a time. Aquarium Science pairs yellow new leaves with nitrogen instead, which contradicts both Aquasabi and the general rule above.

How to fix it

• CO2: check it with a drop checker, and replace the fluid every four to six weeks, as Aquasabi advises. Our CO2 injection page explains the colours.
• Nitrogen or potassium: test and top up. Aquasabi gives optimal ranges of about 10 to 25 mg/l of nitrate and 5 to 10 mg/l of potassium, and warns that most nitrate tests are hard to read. If several macronutrients are short, it suggests a combined macro fertiliser.
• Iron: add a little more complete iron fertiliser. Don’t overdo it: Aquasabi warns that too much can encourage red algae such as black beard algae.
• Light: if only one group of plants is affected, Aquasabi says shading by other plants or decor is a common cause.

Go gently with fertiliser. Tropica’s advice is to start below the recommended dose and raise it as the plants respond.

Preventing it

New plants arrive with nutrients from the nursery. Tropica uses no fertiliser, or only a little, for the first 3 to 4 weeks. Aquarium Science waits much longer, typically three to six months. After that, match fertiliser to light: Aquasabi says more light raises nutrient demand, and an imbalance follows if you don’t top up. Plants Tropica rates medium or advanced need added CO2; the plant ratings chart lets you check yours. And remove dead leaves, which Tropica says can feed nutrient imbalances and algae.

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Yellowing leaves questions

Why are my aquarium plants turning yellow?

Usually a nutrient shortage, though Aquasabi says to rule out a lack of CO2 first. Yellowing in older leaves points to nitrogen, magnesium or potassium, and yellowing in new shoots points to iron.

Why are the new leaves on my aquarium plants yellow?

Aquasabi links yellow-to-white new shoots to iron deficiency, clearest on fast-growing stem plants. Adding a little more complete iron fertiliser usually fixes it.

Should I remove yellow leaves?

Remove leaves that are dead or decaying. Tropica says decaying plant matter can contribute to nutrient imbalances and algae. On new plants, expect some leaves grown above water to die back before new underwater leaves replace them.

Sources: Aquasabi, Deficiency symptoms in aquatic plants; Cornell University, Macronutrient mobility; Tropica, Care; Tropica, Fertiliser and CO2; Tropica, FAQ; Tropica, Starting a new aquarium; Aquarium Science, Planted aquariums in depth; Aquarium Science, Estimative index; Aquarium Science, Algae in low tech tanks.

Green spot algae are the small, hard green dots that appear on aquarium glass and on slow-growing leaves like Anubias. Aquasabi links them to phosphate that is either too low or too high, and a blade scraper and snails keep them in check. Some always turn up, so the aim is control rather than zero.

How to recognise it

Aquasabi describes flat, tiny green spots that start out looking like polka dots and are attached very strongly. Given the chance, they widen into coats. They grow mostly on the glass, but also on equipment, decor and long-lived leaves, especially Anubias.

The test Aquasabi gives is how it comes off. Other green coats don’t start as distinct spots, and some wipe away with a finger. Green spot algae won’t: you need a blade. Aquarium Science disagrees on this point, saying it cleans off relatively easily and treating it as the same thing as green coat algae. Dark, bristly tufts on the same slow-growing leaves are black beard algae, which needs a different fix.

What causes it

Aquasabi finds it most often in strongly lit tanks, and says it usually appears when phosphate is too low or too high. It also notes that a shortage of phosphorus can cause spot algae to increase.

Aquarium Science adds a complication. It says green spot algae will grow slowly with almost no nutrients, and that it can also thrive under heavy fertilising. Treat phosphate as the first thing to check, not the only one.

How to fix it

Start with a phosphate test, then act on the reading. These are Aquasabi’s figures:

Phosphate reading	What Aquasabi suggests
At the lower limit of the test	Add phosphate with a fertiliser
Around 0.1 to 1 mg/l	The recommended range for a planted tank
Around 3 mg/l or above	Bring it down with large water changes, or a phosphate-binding filter medium for a while

If you already dose phosphate, Aquasabi says to cut the dose to match your readings. Then scrape the glass clean with a blade. That way any new spots show you whether the change has worked.

Snails do the rest. Aquasabi rates sun snails and nerite snails as the most efficient grazers for spot algae, rasping the hard coats off thoroughly.

Keeping it under control

Aquarium Science says green spot algae are found in every aquarium, so a few spots are normal. Aquasabi’s routine is to change around 50% of the water each week to stop nutrients building up, scrape the glass as part of weekly maintenance, and keep snails in the tank.

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Green spot algae questions

Does green spot algae mean too much phosphate?

Not necessarily. Aquasabi says it appears when phosphate is too low or too high, and that a phosphorus shortage can make it spread. Test before you dose anything.

How do you remove green spot algae from glass?

Scrape it off with a blade cleaner. Aquasabi says spot algae are always hard to remove, which is one way to tell them from softer green coats that wipe off.

Do snails eat green spot algae?

Yes. Aquasabi rates sun snails and nerite snails as the most efficient algae eaters for spot algae. They rasp the hard coats off thoroughly.

Sources: Aquasabi, Green spot algae (GSA); Aquasabi, Algae in the aquarium; Aquasabi, Green algae coats; Aquasabi, Algae eaters; Aquasabi, Deficiency symptoms in aquatic plants; Aquarium Science, Green spot algae; Aquarium Science, Algae in high tech tanks.

Cyanobacteria, sold to hobbyists as blue-green algae or slime algae, are bacteria rather than algae. They form slimy dark green to near-black coats on plants, hardscape and substrate that lift off easily. The sources disagree on what causes them, so check nutrients, flow, temperature and feeding before you reach for any treatment.

How to recognise it

Aquasabi and Aquarium Science agree it isn’t an alga at all: cyanobacteria are bacteria that photosynthesise. In the tank they show up as dark green, blue-green or almost black coats that feel slimy. Aquarium Science adds that they can also be yellow-green, reddish brown or purple.

Two quick tests help. It doesn’t attach firmly, so Aquasabi says small patches siphon straight off, unlike most true algae. Smell is less reliable: Aquasabi calls the foul, earthy odour characteristic, but Aquarium Science says it is very common for it to have no smell at all. A small patch where the substrate meets the front glass is normal, in Aquasabi’s view, and nothing to worry about. If what you have is green threads, see hair algae. Dark, bristly tufts that grip hard are black beard algae.

What causes it

There is no single agreed cause. Each source points somewhere different, and they overlap on only one thing: high phosphate.

Suspected cause	Who says so
High phosphate, sometimes with low nitrate	Aquasabi; Aquarium Science lists high phosphate too
Too few competing microbes, most often in a new tank	Aquasabi
Overfeeding in fish tanks	Tropica
Low flow, high temperature and low oxygen	Aquarium Science
Old aqua soil that has crumbled and compacted	ADA

Aquarium Science adds two caveats: some outbreaks happen with none of these present, and cyanobacteria are found almost everywhere, so you can’t keep them out of a tank entirely.

How to get rid of it

• Siphon it off during a water change. Small patches come away easily.
• Feed less. Tropica says less intense feeding usually makes it disappear again.
• Raise flow and oxygen, and lower the temperature. Aquarium Science’s fix is more water movement, a cooler tank, surface agitation, and large water changes to bring phosphate down. It says a 95% water change is harmless to fish.
• Check the substrate. ADA says blue-green algae can grow in aqua soil that has crumbled and packed down, and the answer then is to rebuild the substrate. Our aquasoil page covers how soil breaks down.

For a stronger infestation, Aquasabi recommends a blackout: siphon off as much as you can, switch off CO2 and liquid fertiliser, keep the tank well aerated, and keep it dark for no more than 7 days if it holds stem and carpet plants, or up to two weeks if it mostly holds shade plants.

Treatments the sources argue about

Three treatments come up, and each has a source against it. Aquasabi recommends bacteria products to restore the microbial balance, which Aquarium Science calls a myth. Aquasabi uses hydrogen peroxide as a last resort. Aquarium Science says never to use chemicals other than antibiotics on cyanobacteria, and warns that antibiotics only work for a while and can spike ammonia and nitrite in an established tank.

Aquarium Science’s conclusion is the one to hold on to: any treatment gives only temporary respite, and the cyanobacteria come back unless you remove the cause.

Keeping it away

Change water regularly: Aquasabi recommends around 50% a week to stop nutrient spikes. Keep feeding moderate, keep the tank within the 20 to 26°C range Aquarium Science gives as ideal for plants and fish, and keep water moving across the substrate. In a soil tank, replace the soil once it has broken down.

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Blue-green algae questions

Is blue-green algae actually algae?

No. Both Aquasabi and Aquarium Science say it is a bacterium, cyanobacteria, that photosynthesises like a plant.

Does a blackout kill blue-green algae?

Aquasabi recommends a blackout for stronger infestations, with CO2 and fertiliser off and the tank well aerated, for no more than 7 days in a tank with stem and carpet plants. Remove as much as you can by siphon first.

Why does blue-green algae keep coming back?

Because the cause is still there. Aquarium Science says chemicals and antibiotics give only temporary respite. Look at phosphate, feeding, flow, oxygen and temperature, and at the state of the substrate.

Sources: Aquasabi, Blue-green algae (BGA); Aquasabi, Algae in the aquarium; Aquasabi, Black-out treatment; Aquasabi, Treatment with hydrogen peroxide; ADA, Aqua Soil Amazonia (via Aquasabi); Tropica, Types of algae; Aquarium Science, Blue-green algae; Aquarium Science, Algae in high tech tanks.

Hair algae is the green, hair-like growth that coats plants and hardscape, most often in a tank only a few weeks old. Aquasabi separates true hair algae, which anchors firmly, from loose thread algae, while other sources use the names for the same thing. The fix is the same for both: balance light, CO2 and nutrients, and add grazers.

Hair algae or thread algae?

The names get mixed up, and it matters a little for removal. Aquarium Science uses “thread algae, hair algae or green hair algae” interchangeably and warns that identifying the exact species is a guess. Aquasabi splits them by how they attach, which is a useful test in your own tank.

	Hair algae	Thread algae
Growth	Carpet-like coats of short, dense filaments	Long, soft, loose threads in bushy cushions
Attachment	Anchors its base tightly	Doesn’t attach, wraps around plants
Spreads by	Growing over plants and decor	Fragments drifting in the current
Removal	Hard to pull off; cut infested leaves	Wind onto a rough skewer or siphon out

One look-alike to rule out is Cladophora. Aquasabi describes it as short, rigid green filaments that branch in many places, with a smell like mushrooms. Two other growths get mistaken for it: a dark, slimy film that siphons straight off is cyanobacteria, and hard green dots on the glass are green spot algae.

What causes it

The most common trigger is a new tank. Aquasabi says hair algae appear mainly during the cycling phase, and that thread-like green algae usually follow the diatoms 3 to 4 weeks after set-up.

In an established tank it points to an imbalance. Aquasabi names a shortage of CO2 or nutrients, nitrogen in particular, along with lighting that is too strong or left on too long. A new, brighter light or extra daylight can set off a sudden outbreak, and so can slack maintenance. Tropica adds heat: temperatures above about 26°C almost always cause algae problems, and thread algae especially likes warmth. Its general rule for any algae is that overfeeding comes first.

How to get rid of it

• Remove what you can: cut off lightly infested leaves, wind thread algae onto a rough skewer, and siphon out loose nests during a water change.
• Fix the imbalance: check CO2 with a drop checker, which Aquasabi says to refill every four to six weeks, and top up nitrogen if plants have stalled. Our CO2 injection page covers reading one.
• Add grazers: Aquasabi calls the Amano shrimp the most efficient shrimp for filamentous algae, and Tropica suggests a large population of them for a while during an outbreak.
• Change more water: Tropica suggests 30% every second day for a period.
• Plant more: if the tank is sparsely planted, Aquasabi recommends adding healthy, fast-growing plants to compete.

A heavy infestation may need a blackout. Aquasabi turns off CO2 and stops liquid fertiliser, keeps the tank dark for up to two weeks if it mostly holds shade plants such as mosses, ferns, Anubias and Cryptocoryne, and no more than 7 days if it holds stem and carpet plants, then does a large water change. Tropica’s blackout, given for green water, is much shorter at 2 to 3 days. Start with the shorter one.

Chemicals are the last resort

The sources split here. Aquasabi spot-treats small patches with hydrogen peroxide and treats the whole tank with an algicide only as a last resort, warning that algicides can upset the tank’s microbial balance and harm some plants, and that at least one kills nerite snails. Tropica generally recommends not removing thread algae with chemicals, and Aquarium Science doesn’t recommend chemicals at all. If you go that way, follow the source’s own dosing exactly, and fix the cause first or it comes back.

Keeping it away

Plant heavily from the first day, with plenty of fast-growing stem plants. Keep the lights short in a new tank: Tropica starts at 6 hours a day for the first 2 to 3 weeks before moving to 8 to 10, and recommends never more than 10 hours, on a timer. Aquasabi adds that more light always needs more nutrients to match. For weekly water changes, Aquasabi recommends at least 50% and Tropica about 25% once a tank is established. Our lighting page covers choosing a level to begin with.

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Hair algae questions

Do Amano shrimp eat hair algae?

Yes, the softer kinds. Aquasabi calls the Amano shrimp the most efficient shrimp for filamentous algae, and says ramshorn snails and most dwarf shrimp also eat softer hair algae.

Why does a new tank get hair algae?

Because the tank’s biology hasn’t settled yet. Aquasabi says hair algae appear mainly during the cycling phase and usually clear on their own once nutrients are balanced and enough algae eaters are in the tank.

How long should a blackout for hair algae last?

Sources differ. Tropica suggests 2 to 3 days. Aquasabi allows up to two weeks in a tank of shade plants but no more than 7 days if it holds stem and carpet plants. Either way, do a large water change afterwards, because the dying algae pollute the water.

Sources: Aquasabi, Hair algae; Aquasabi, Green thread algae; Aquasabi, Algae in the aquarium; Aquasabi, Cladophora; Aquasabi, Black-out treatment; Aquasabi, Treatment with hydrogen peroxide; Aquasabi, Algae eaters; Aquasabi, Fertilization during the cycling phase; Tropica, Types of algae; Tropica, Algae control; Tropica, Preventing algae; Tropica, Starting a new aquarium; Aquarium Science, Thread algae; Aquarium Science, Controlling aquarium algae.

Black beard algae is the dark, bristly growth that grips plant edges, wood and equipment in planted tanks. It is a red alga, sold and discussed under the names black beard or brush algae. It is stubborn rather than dangerous, and it almost always points to something specific being off in the tank.

What it actually is

Black beard algae covers species in the genera Audouinella and Rhodochorton. It attaches hard to surfaces rather than drifting, which is why wiping does so little and why it tends to colonise the slowest-growing leaves first. Older Anubias leaves are a classic site. If the growth is green and soft rather than dark and bristly, it is more likely hair algae. Hard green dots are green spot algae, and a dark, slimy film that lifts off easily is cyanobacteria.

Why you have it

There are three well-documented causes, and they point at different tanks.

• Organic pollution: in tanks with a heavy fish stock and few or no plants, the black variant is common. The cause there is high organic pollution from overfeeding combined with too few water changes.
• CO2 shortage: where CO2 is short, these algae can take the carbon they need from hydrogen carbonate, and they do it far more easily than higher aquatic plants can. That is the mechanism behind the usual advice that unstable or insufficient CO2 brings on black beard algae. Your plants stall, the algae does not.
• Nutrient imbalance: in properly planted tanks it often appears when micronutrients are out of balance, iron in particular.

Work out which tank you have before you treat anything. A heavily stocked, lightly planted tank has an organic waste problem. A high-tech planted tank creeping with it has a carbon or nutrient problem.

Getting rid of it

Liquid carbon is the usual first move. Dose per the manufacturer’s instructions and the algae should turn whitish or pink within a few days, which is the sign it is dying rather than a trick of the light.

If that does not clear it, treat the affected spots directly rather than the whole tank. Spot dosing an algicide or hydrogen peroxide onto the growth is the targeted version of the same approach, and it works on patches that whole-tank dosing leaves behind.

Neither is a fix on its own. If the underlying cause is still there, it comes back. Sort the feeding and water changes, or stabilise the CO2, and the treatment gets to stay ahead of it.

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Black beard algae questions

Is black beard algae harmful to fish?

No. It does not harm fish or shrimp. The damage it does is to plants, by covering leaves and blocking the light they need, and to your patience.

Why does black beard algae keep coming back?

Because treating the growth does nothing about the cause. If the tank still has excess organic waste, unstable CO2 or a micronutrient imbalance, new growth follows the old. Fix the condition first and treat second.

Should I throw away plants covered in black beard algae?

Usually not. Badly affected old leaves are worth removing, since slow-growing plants rarely recover a heavily colonised leaf, but the plant itself normally recovers once conditions improve and it pushes new growth.

Sources: Aquasabi, Black beard algae (BBA).

Aquarium plants melt when they drop their leaves in the weeks after planting. It looks like the plant is dying, and usually it isn’t. Most shop plants were grown out of water, and those leaves can’t survive submerged, so they die back while new underwater leaves replace them. Leave the roots in place and wait.

Why aquarium plants melt

Most plants come from the nursery in their emersed form, grown with their leaves in the air. Buce Plant explains why: grown that way, plants grow much faster, stay largely free of algae and survive shipping better. Aquasabi says they then have to adapt to life underwater, which takes quite a bit of time, and it isn’t unusual for a plant to lose all its old emersed leaves on the way.

That leaf loss is the melt. Buce Plant says the emersed leaves aren’t adapted to survive underwater, so they slowly decompose while new submerged leaves grow to replace them.

What plant melt looks like

Old leaves go, then leaves adapted to underwater life grow.

Tissue-culture plants

Plants sold in cups from in-vitro culture behave a little differently. Aquasabi says they are generally somewhat more sensitive than potted emersed plants, but usually need only a few days to get used to a tank. Expect slow or stalled growth and perhaps the loss of adult leaves, especially in Cryptocoryne and Bucephalandra. Brown leaves already in a Cryptocoryne cup are normal, Aquasabi adds.

Other things that cause melt

The move to water is the usual cause, but not the only one. These are the others the sources name:

• Rough handling. Buce Plant says damage in shipping, or fish chewing the leaves, can set it off.
• An uncycled tank. Buce Plant warns that nutrient-rich aquasoil can leach ammonia into a new tank, and recommends planting into a cycled one.
• Too little light or too few nutrients. Once a plant has made the switch, Buce Plant says melt can point to a nutrient shortage, and that too little light can cause it too.
• Sudden changes. Horizon Aquatics says crypts are sensitive to sudden changes in pH, temperature, hardness and light. Buce Plant adds that a big switch in water chemistry, or very hot or cold water in a large water change, can trigger mass melt in a carpet.
• Moving the plant. Buce Plant says a plant moved before it has rooted has to start again, and may melt while it does.

Which plants melt

Plant	What the sources say
Cryptocoryne	Almost all species do it (Buce Plant), often within days of going into a new tank (Horizon). It is so common that it has its own name, crypt melt. Cryptocoryne parva is the exception: Buce Plant says it usually doesn’t melt like the others.
Bucephalandra	Tissue-culture plants may lose their adult leaves (Aquasabi).
Monte Carlo and other carpets	Some melt at first is normal, and new growth replaces it if conditions are right (Buce Plant).
Hornwort	Sheds its needles after sudden changes, temperature swings or a move (Buce Plant). It grows only underwater, so it has no emersed leaves to lose.
Anubias	Tropica says Anubias grow so slowly they barely notice being submerged. If one loses leaves, check the rhizome isn’t buried: Tropica says that makes the whole plant rot and die.

The one mistake that kills the plant

Digging it up.

A melting plant usually is not dying, so there is nothing to rescue. Horizon Aquatics says the roots often survive crypt melt and new leaves will sprout as long as they are healthy, and Buce Plant says a crypt with healthy roots that isn’t moved should show new growth within a few weeks. Pulling a melting Cryptocoryne wendtii out to inspect it, or moving it somewhere it might be happier, sets that back.

The same applies to rhizome plants. Aquasabi says even a bare rhizome, with no leaves or roots left, can grow back into a whole plant if it is intact. Keep it attached to its wood or rock and wait.

What to do while it melts

• Remove the dead leaves. Horizon Aquatics says decaying leaves can cause ammonia spikes, and Buce Plant says rotting leaves add nitrate that can lead to algae.
• Leave the roots and rhizome in place. This is the whole trick.
• Keep conditions stable. Horizon advises avoiding further changes for a few weeks.
• Wait. Aquasabi’s advice is not to give up on plants too early, because they usually bounce back.

How to reduce it next time

You can’t always stop melt, but Buce Plant gives several ways to cut it down:

• Plant into a cycled tank, so ammonia from fresh soil isn’t added to the stress.
• Trim off a few emersed leaves before planting, and remove the rest once plenty of submerged growth has appeared. With crypts, Buce Plant suggests cutting off all the emersed leaves, except on Cryptocoryne parva.
• Don’t move plants once they are in.
• Keep the routine steady: feeding, water changes and light hours.
• Add CO2 if you can. Buce Plant says it shortens the transition, and helps melting crypts bounce back faster.

Aquasabi adds two tips for a new tank: start with only a little fertiliser while the plants adapt, and plant at least one group of fast stem plants that are already in their submerged form, as an early warning of any deficiency.

How long it lasts

For potted plants, weeks. Aquasabi’s timeline for a new tank says plants should have taken on their submerged form, rooted and started growing visibly by week three. Buce Plant says crypts that keep healthy roots should show new growth within a few weeks. Tissue-culture plants are quicker, usually a few days according to Aquasabi.

When it is not melt

Melt happens shortly after planting and affects the existing leaves while new growth appears. If an established plant starts declining months in, that is a different problem and the place to look is light, nutrients or CO2 rather than transition. Our yellowing leaves page covers how to read the pattern.

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Questions about melting plants

Why are my aquarium plants melting?

Usually because they were grown out of water. Buce Plant says emersed-grown leaves aren’t adapted to life underwater, so they decay while new submerged leaves grow. Sudden changes in water, light or temperature, and moving a plant, can also set it off.

How long does plant melt last?

A few weeks for most potted plants. Aquasabi expects plants in a new tank to be growing visibly by week three, and Buce Plant says crypts with healthy roots show new growth within a few weeks.

Will melted aquarium plants grow back?

Usually. Horizon Aquatics says the roots often survive crypt melt and new leaves sprout while they are healthy, and Aquasabi says even a bare rhizome can regrow if it is intact.

Should I remove a melting plant from the tank?

No. Take off the dead leaves and leave the roots where they are. Moving a plant before it has rooted makes it start again, Buce Plant says.

Can you prevent plant melt?

You can reduce it. Buce Plant’s advice is to plant into a cycled tank, trim emersed leaves before planting (except on Cryptocoryne parva), leave plants where you put them and keep conditions stable.

Sources: Aquasabi, Fertilization during the cycling phase; Aquasabi, Appearance of in-vitro plants; Aquasabi, How to trim and divide aquatic plants; Buce Plant, How to prevent aquarium plant melt; Buce Plant, How to prevent Cryptocoryne melt; Buce Plant, How to grow aquarium carpet plants; Buce Plant, Hornwort (shop listing); Horizon Aquatics, Cryptocoryne and crypt melt; Tropica, Anubias barteri ‘Coffeifolia’; Tropica, Anubias gracilis.