Will algae killers harm my shrimp?

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Are shrimp sensitive to algae growth retardants? A reader asks...

Q) I keep a variety of tropical fish in a 56 l tank, such as Corydoras catfish, tetras and Harlequins. I would like to add some small shrimp species, but when it comes to using algae growth retardants, is there any caution as to the product to use? Are shrimp sensitive to these products?

GRANT DAVIES, VIA EMAIL

 

A) Neale says: While some of the algae-removing chemicals are certainly toxic to algae while harmless to plants, their toxicity to shrimps and snails will vary. The one made by API, for example, says right on the bottle that it’s toxic to freshwater crustaceans, which would of course include shrimps as well as crabs and crayfish. I’d assume all are toxic to shrimps unless it says on the bottle that it is shrimp-safe, and even then, I’d remove a few of the shrimps to another aquarium just in case things go badly.

No matter how you kill or remove the algae in the tank today, if conditions aren’t otherwise changed, it will be back in a matter of days or weeks. Algae is highly invasive, and where conditions suit, it will grow.

But it can be managed. The simplest solution is to add plenty of fast-growing plants, such as Hygrophila, to your aquarium, ensure conditions are ideal for them, and let the plants take care of the algae for you by using up the nutrients the algae needs to grow. If you have plants growing quickly enough that you’re removing handfuls every week or two, you’ll find algae problems generally don’t develop.

If the only plants you have are slow-growing species like Anubias, Bucephalandra and Java ferns, these aren’t going to do any of the heavy lifting required to suppress algae. Indeed, slow-growing plants tend to become smothered with algae, particularly if placed in direct light. Both Anubias and Java ferns prefer to be positioned underneath floating vegetation, so that they receive moderate or indirect light only.

In some cases growing plants quickly enough may require upgrading the installed lighting system, replacing a gravel substrate with one that’s richer in minerals, or even installing a carbon dioxide (CO2) fertilisation system. But floating plants are indifferent to the substrate used and don’t need extra CO2 (since they get it from the air) so if you choose floating plants, controlling algae can be simple. Floating Indian fern is probably the best all-rounder, but can be harder to get than another adapted species, Amazon frogbit. Unless your aquarium has a very well ventilated hood, I’d avoid the more sensitive species like Salvinia that are sensitive to burning under hot lights.