Do fertilizers hurt livestock?

Most fish/shrimp are not sensitive to fertiliser in the normal doses required for plant growth. Most fertilisers are made up of common elements found in natural waters. Commercial brands do not introduce them in high enough concentrations to affect the animals. For commercial brands, the recommended dosage rates generally have such a wide safety margin that even a 10-fold overdose will not harm livestock. In controlled drop tests we have carried out on Neocaridina shrimp, a 10x overdose of common fertilisers such as Seachem Flourish Comprehensive had no effect on the shrimp.

Some aquarists are concerned about copper in fertilizers; however, commercial aquatic plant fertilizers contain only minute amounts of copper - far too small to be harmful. 

The exception to this scenario is people who make their own fertiliser mixes using fertilisers calibrated for terrestrial plants. Excessive levels of heavy metals in trace element packets could affect 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 VOCs and ammonia from the substrate can kill fish/shrimp/snails and other animals. Therefore, extra care should be taken when replanting or moving hardscape in mature tanks. A major water change after replanting is generally good practice.

Does APT contain copper?

Yes, in minute amounts, 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.

CO2

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.

other parameters

When doing water changes, check that the key water parameters are similar: TDS, GH, KH, temperature. Always remember to use dechlorinated water.