"How do I know if there is too much algae in an outdoor fish pond or pot?" tracks the potential issues with too much algae in my fishes environment.

I keep goldfish outdoors in large, ceramic pots, approx 50 cm in diameter x 80 cm tall. The pots contain pond weed, and there is some algae on the inside of the pots, but it hasn't seemed to bother the fish up to this point.

I have been considering purchasing snails from the local fish shop (aquarium, not fish and chip shop :) ). I have a some concerns:


2 Answers 2


Your pot has, more or less, 60 liters of water, so I'll make some analogy with a 60 liters aquarium.

1 - If you're purchasing the snails, I assume that they are those desirable, pet snails, which tend to be bigger (from 2 up to 3 inches). So one would be enough.

  • Although most snails are hermaphrodites, they need to mate to reproduce. So, having just one snail would prevent that overabundance

  • Some snails, like apple snail, have separated sexes, so you could have more than one if you choose only males or females. And males would be more desirable, because females can store the sperm from a previous relationship for months, and perhaps the fish store might not know about her past. :)

2 - Snails, in general, will eat your vegetation. Depending on the plants you have (like softer ones), they will prefer to eat plants instead of algae, and might have the opposite effect than you planned.



Without knowing more about your climate and water conditions, it's impossible to make an effective guess as to what fish or crustaceans would be suitable for eating algae while also being able to survive the outdoor conditions and goldfish for tank mates. Turn to manual removal or goldfish-safe algaecides instead.


While some snails will eat algae, most species aren't usually ideal options for anything more than minimal algae control, especially in unfiltered pots or ponds in outdoor conditions. In addition, the goldfish would likely eat anything that would manage the algae, including small snails or shrimp, so it's likely that you'd be better off just adding some algaecide to the pots from time to time, but you have to know what kind of algae you're dealing with as each may require a different approach.

Barley bales or barley extract are often used in ponds to reduce algae and support the nitrogen cycle, but your pots are likely too small for that. Flourish Excel, which is actually marketed as a plant supplement, also acts as an algaecide for many common forms of algae. For small pots, though, it's probably easier just to manually wipe away the excess algae when you do a water change.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.