Why Copper-Based Medication Kills Shrimp and Snails

Written 2026-11-04

Copper-based medications like ich treatment cure fish, but even a small amount is lethal to invertebrates such as shrimp and snails. Running it in the Water Kiwoogi simulator shows the shrimp and snails die the moment the dose goes in, while the fish in the same tank stay completely healthy. That’s why invertebrates need to be moved to a separate container before using a copper-based medication.

Same 60cm tank, same medication — only the invertebrates die

We cycled a 60cm tank fishless with ammonia solution, finishing on day 24, then stocked 6 glowlight tetras, 10 cherry shrimp, and 3 nerite snails on day 28. Starting on day 42, we dosed copper-based ich medication exactly as the catalog describes — three doses, three days apart. The moment the first dose went in, all 10 cherry shrimp and all 3 nerite snails died on the spot. The 6 glowlight tetras that got the same dose stayed alive through day 60. Run the same tank with only the tetras — no shrimp or snails at all — and nothing dies through day 60.

Waiting or dosing less doesn’t help

In this model, copper kills every invertebrate in the tank the instant it’s dosed, no matter how stable the water is or how low nitrate sits. There’s no safe way to try a small dose and see, or to treat for just a few days while they’re still in there — once the medication goes in, it’s immediate. The only way to protect shrimp, snails, or crayfish is to move them out before treatment starts.

Which invertebrates does this apply to?

Anything the catalog marks as an invertebrate gets the same treatment — shrimp like cherry, amano, crystal, and native shrimp; snails like nerite, ramshorn, Malaysian trumpet, and apple snail; and the dwarf orange crayfish (CPO) too. It doesn’t spare some species over others. Fish and non-invertebrate bottom dwellers like corydoras aren’t affected by this at all.

The filter bacteria take a hit too — watch your water during treatment

Copper-based medication doesn’t just target invertebrates — it also kills 25% of the filter bacteria colony with every dose. In this tank the colony was large enough that even after all three doses (roughly a 60% cumulative loss), ammonia and nitrite stayed at zero. In a newer tank, or one that’s more heavily stocked, it’s safer to keep testing ammonia and nitrite while treatment is underway.

The button below links to this guide’s example — a 60cm tank with only 6 glowlight tetras (shrimp and snails already removed), under treatment.

The numbers in this guide come from the Water Kiwoogi simulator model; real tanks can differ.