Most fish/shrimp are not sensitive to fertilizers in the normal dosages that is required for plant growth. Most fertilizers comprise of common elements available in natural waters. Commercial brands do not introduce them in high enough concentrations to affect livestock. For commercial brands, the recommended dosage rates generally have so wide a safety range that even a 10 times overdose does not harm livestock. In controlled drop tests we conducted on neocaridina shrimp, a 10X overdose of common fertilizers like Seachem Flourish comprehensive had no affect on the shrimp.
Some aquarists have concerns over copper in fertilizers; however, commercial fertilizers for aquatic plants only contain copper in minute amounts - far too minute to be harmful.
The exception to this scenario are folks that DIY their own fertilizer mixes by using fertilizers calibrated for terrestrial plants. Over-loading greatly with heavy metals found in trace element packs could impact livestock.
It is common for planted tanks to keep shrimp. They consume detritus and breakdown organic waste and are a useful addition to any planted tank.
But my fish / shrimp / snail etc died after adding fertiliser?
It is common for new livestock to appear fine for a few days after being introduced to a tank, and then suddenly die. In many cases, outwardly healthy livestock may already be injured and damaged internally. Experienced hobbyists almost always choose to buy livestock only from trusted sources, due to the difficulty in assessing livestock health from outward view alone.
In mature tanks, the release of volatile organic matter and ammonia from the substrate can kill fish / shrimp / snails and other livestock. So extra care should be taken when replanting or shifting hardscape in mature tanks. Doing a larger water change after replanting is generally a good practice.
Does APT contain copper?
Yes, in tiny, chelated form.
But isn’t copper harmful?
The amount of copper in APT is so tiny that it is basically harmless. Copper can indeed kill- in the way that the electricity from a 120V AC socket can. But a 1.5V DC battery is quite different.
But isn’t it still copper?
The minuscule amount of copper in APT is in chelated (i.e chemically bonded) form that makes it digestible by plants, but harmless to livestock as it is in a different molecular structure. Chelated copper is also a common food supplement. Think of it as a 1.5V DC battery with an additional rubber casing.
Why have it at all?
Because in the correct structure and trace amounts, copper is both essential and beneficial to plant and livestock health.
However, livestock can be sensitive to high CO2 levels and instabilities such as rapid changes of water parameterscaused by large water changes when the tap water is different from tank parameters.
High CO2 rates can affect brood rates for CRS shrimp. Large flux due to water changes can cause excessive moulting. Neocaridinas are much more tolerant.
When doing water changes, check that the key water parameters are similar: TDS, GH, KH, temperature. Always remember to use dechlorinated water.