Ammonia

The two pictures above are examples of Ammonia detectors (ok, I have all of them to detect/test for Ammonia).

I usually place Seachem's Ammonia Alert (second picture) in my overstocked aquariums for convenience - to continuously detect any changes (for upto a year) in the ammonia level in each tank and I find it quite sensitive. The cost is a bit prohibitive (but remember it last a year) and it may take around 15 minutes or more (if I remember it right) to level off after higher readings (and upon refilling the aquarium with fresh water during water changes).

An alternative are the API Ammonia Aquarium Strips (right most in first picture) for those who are a bit lazy like me. With 25 test strips, it cost less than half of Ammonia Alert. The most affordable are the test solutions.

So what does one do if these test kits are not available? Simple, just follow what I do most of the time, when in doubt, do 'water change.' Oftentimes, the 'intuition' that something is wrong is right especially if one is a keen observer specially of fish behavior.

Other clues that will make one suspect some problems (read higher ammonia levels than usual) relate to the effects of ammonia on the fish nervous system and gill membranes. These include spasms (jerks for example), erratic movements and eventually losing their balance, swimming to the surface and sinking to the bottom later and dying. Another clue is water cloudiness, although this is often thought to be ammonia - it is actually the effect of increased in heterotrophic bacteria population which is due to the availability of ammonia in the water.

Long term effects of ammonia toxicity includes lesser growth rates, susceptibility to gill membrane bacterial infection, organ damage, and even abundant secretion of mucus.

It is important to note here that, there are differential effects of ammonia to different fish species, meaning, each fish species will have differing tolerance and toxicity will depend on this. In general though, one again should remember that ammonia is toxic even at very low levels and its presence only indicates that the biofiltration system isn't working properly or even inadequate. Addition of rock salt was found to effective in lowering the effects but is less than the degree afforded by calcium chloride.