Discus Enemies One and Two
By: Robert Clough
Jun. 02, 2000

In my more than eighteen years of keeping and breeding discus, the most common cause of discus health problems is incorrect water conditions. Fish keeping is not about fish. It is about water chemistry. If your water chemistry skills are not honed to a sufficiently knowledgeable level then you are doomed to failure. I will only discuss two elements of the large family of water chemistry components here but I strongly advise that you learn as much as you can about water chemistry in general. Your fish will live a lot longer and you will enjoy your hobby a lot longer if you take the time to do the research.

By far the two most deadly substances in discus water are ammonia compounds and nitrite. Unfortunately, for a biological filtration system to function correctly, both of these compounds must be present and must also be chemically converted to the end product-nitrate-very fast and efficiently by the filter.

For those of you that are new to discus keeping, your biological filter is NOT the filter media but the nitrifying bacteria that inhabit the media. I do not propose to describe how a biological filter works as there are numerous articles available for that purpose. What I do want to discuss is how to RECOGNISE and TREAT symptoms of ammonia and nitrite poisoning. I will not bore you with the chemical reactions of both these toxins as they are very complex.

Before we get involved in the fun part, let me just say this. Do not be lulled into a false sense of security by believing that ammonia is non-toxic in acidic water. Nothing could be further from the truth. I have killed fish with ammonia in tanks with a pH as low as 3.8!!!. Also, the higher the tank temperature the more toxic the ammonia. Scary stuff indeed.

If I was asked to pick the one task that was most neglected by fish keepers I would have to say it is the simple job of testing their tap water or whatever water source they use to change their tank water with PRIOR to EVERY water change. With all the health-benefiting chemicals that our water supply authorities dump in our tap water, the acid rain that we collect and the contaminated river/lake/bore water that we use, I will guarantee you that you will introduce certain death into your tanks if you do not monitor it at every water change.

Chloramine-a combination of ammonia and chlorine-is routinely added to our tap water. Good quality activated carbon and the correct water flow rate over this carbon will eliminate chlorine but will NOT eliminate ammonia. If you detect even the slightest amount of ammonia or nitrite in your tap water you must use appropriate chemicals to detoxify them BEFORE adding the water to your tanks. There are several products on the market that will do this. The products that I use and recommend are Seachem's "Prime" and "Safe". I could not keep my fish alive in my tap water without these products as it is always loaded with one or both toxins. Prime is most suitable as it does not need pre-mixing. I strongly recommend that you keep some form of ammonia and nitrite detox on hand for that emergency. Zeolite is very good for removing ammonia but it won't take care of nitrite and it needs to be regenerated or thrown out after it has adsorbed it's fill of ammonia. Please note that both ammonia and nitrite will pass through reverse osmosis membranes and certain deionising resins will remove ammonia.

The main source of ammonia in your tank will come from the fish's gills-assuming you're not grossly overfeeding. If there is sufficient ammonia in the tank, your fish will not be able to excrete ammonia through their gills and will be poisoned-either very slowly or extremely fast.
The larger your fish the more resistant to ammonia poisoning it will be. As an example, your breeding pair may behave normally as your wrigglers begin to free-swim but the fry will go straight to the top of the tank trying to breathe and will be dead within two hours or sooner. This can happen with such a small amount of ammonia in the tank as to be undetectable by test kit. This can be overcome with the use of detox chemicals and by changing as much water daily as you can. Be sure to have the temperature, pH and hardness as near to the same as the tank water as you can. I have taken wrigglers on the pipe and their parents and transferred them to another tank without mishap so don't be afraid to change your water.

The symptoms of ammonia poisoning can vary depending on the amount of toxin but it generally begins with a head-up attitude and fast breathing-not necessarily at the top of the tank-followed by a loss of vertical attitude i.e. laying over on their side, a heavy mucous (slime) excretion and fraying of the pectoral and dorsal fins. In bad cases, where the fish has been saved, the fins can disintegrate right back to the body. If this happens do NOT medicate as the fins will grow back rapidly assuming you water parameters are correct. Many people have mistaken these symptoms for the so-called "Discus Plague" although, on two occasions, I have had ammonia spikes in adult holding tanks that appear to have been a precursor to the plague or something very similar to it. I say this because the usual treatment regimen for the plague had no effect on the problem. I digress... that is another story.

Nitrite poisoning has the effect of converting the fish's blood haemoglobin to methaemoglobin which does not allow oxygen to be transported through the blood. Nitrite has the same effect on humans. The symptoms are also a perfect match for those of gill flukes and in numerous cases have been diagnosed as such with devastating results. Fast breathing, clustering together at the tank top, shimmying and pancaking. Nitrite poisoning can be slow acting to the extent that it may take two months for the fish to die from exposure to it. Sea salt or table salt can be added to the tank at the rate of two tablespoons per 40 litres to give temporary relief. The chlorine content of the salt prohibits the nitrite from being absorbed by the gills.
Just a word about how these toxins can be introduced into a tank other than by water changes.

Biological filtration has an optimal pH range for maximum efficiency. Unfortunately this is above 7.4pH. As most of us who keep discus run our tanks under 7.0pH, we need to be careful not to damage the filter. Probably the most dangerous tank condition as far as biological filtration is concerned is a "pH crash". Now this doesn't usually happen fast but takes between 12 and 24 hours. The most common cause of this crash is the nitrifying bacteria itself. They consume carbonates (kH) to perform their duties and if the carbonate hardness of your tank is low-as it should be for breeding purposes in particular-then the buffering capacity or ability to resist change in pH of your tank is gone and your pH falls to dangerous levels. The best way to fix this quickly is to add bi-carb to your tank and raise the pH back quickly. Yes...quickly. You won't hurt your fish by raising the pH from 3.5 to 6.5 in 5 minutes. Don't try reducing your pH quickly though as this is deadly to your fish. I do it quite often because the kH in my breeding tanks is less than one. Trouble starts when you don't attend to this quickly and your filter bacteria start to die off with the resultant buildup of ammonia, nitrite or both.

If you learn to keep your water conditions as they should be, test both your tank and "raw" water at each change-hopefully this is at least every second day, have some form of detox on hand and study the behaviour of your fish you will not suffer the tragic consequences of these two horrendous toxins. Remember, if you are ever in doubt about your tank's condition, test everything and do a water change...then do it all again.

Everything I have written about here has come from hard-won experience...not out of a book.
I have killed more fish out of ignorance and stupidity than most of you will ever keep so if I save just one fish with my ramblings here then it will have been worth it. Feel free to contact me if you need any help.
Take care and good fish keeping.

Australian Discus Breeders