Why Do My Aquarium Plants Rot?

Updated February 21, 2017

Aquarium plants can add visual interest to your tank and provide a number of health benefits for your fish. Fish often like to hide in or swim amongst the foliage, and multicoloured plants make an aesthetically pleasing design statement. All the benefits of aquarium plants will be outweighed, however, if your plants start to rot. A number of reasons can be behind rotting aquarium plants, and the solutions depend on the problem.

Terrestrial Plants

Houseplants and other terrestrial plants will not survive in an aquarium. They will rot, according to Aquarium Pro, as they are not meant to be submerged and their leaves need air exposure to survive. Sometimes stores or dealers will fraudulently sell terrestrial plants as aquarium plants, so research suitable plants before investing. Two common examples of plants sold for aquarium use that should not be included in a tank is the peace lily (Spathophyllum) and the sweet flag (Acorus).

Common Problems

Even if a plant is meant for an aquarium, it can still rot due to a number of problems. According to Badman's Tropic Fish, some common causes include too little fertiliser and too much phosphate in the tank, as well as the gravel or other substrate lacking nutrients or being too fine. The plant could also be suffering from Cryptocoryne disease, also called Crytocoryne rot. Cryptocoryne disease is idiopathic, but it is often made worse by dirty water and lack of proper light and nutrients.


Determine the cause behind your rotting plants by noting the affected plant's particular symptoms. Plants that are suffering from too little fertiliser and too much phosphate will have leaves that turn yellow, brittle, thin and finally rot off. If your plants' roots are rotting and turning black, your tank's substrate may be to blame. Cryptocoryne disease starts with little holes in the leaves and advances with larger holes until it finally breaks down the entire leaf. The disease can take out the whole plant or spread to all the plants in the tank.


Depending on your plants' problems, there are various solutions to stopping or preventing rot. Fix a potassium deficiency and abundance of phosphate by using a fertiliser compound that is high in iron. If you are already using fertiliser, try lowering the carbonate hardness of the water as well as the water's pH with water conditioners. Correct a problem with the substrate by adding coarser material to gravel or sand that is too fine, and use a substrate fertiliser. If that doesn't work, you may need to replace your substrate. Fight Cryptocoryne disease with a massive water change, stirring up and cleaning out the substrate and removing all dead and rotting plant pieces.


General tank care will help keep your plants as healthy as possible. Basic aquarium plant care includes good lighting, a deep layer of substrate, fertiliser for the plants and soft water. Most aquarium plants need more light than a single lamp can provide. Different aquarium plants thrive under different conditions, and some have specific care requirements; prevent plant rot by learning more about your particular plants and providing adequate nutrients and light before you encounter problems.

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