Some test kits read 0 as 0-0.25. But if the pH of the water is 7.0 or less (and it probably is due to the
CO2), then ammonia isn't going to be an issue because it changes into the less harmful ammonium at the lower pH.
Some plant substrates can release ammonia for months or years after they are added to an aquarium. Most stop releasing it after a few months. You might have something rotting under an ornament or even driftwood that is rotting and releasing trace amounts of ammonia.
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White spot does not kill large numbers of fish rapidly unless you let the white spot parasites build up to huge numbers, then one day you find a pile of bodies in the tank. However, you will see the white spot building up on the fish several weeks prior to this happening.
The silver tetra looks like it has excess mucous over its body, so does the rummynose tetra, but it also appears to have white spot. Fish naturally have a thin clear layer of mucous over their body and if they are stressed out by something, they produce more mucous that can appear as a cream, white or grey film over part or all of the body and fins, or it can look like clear filaments hanging from the fish. Normally it's caused by a chemical in the water.
If a number of fish died shortly after a water change, then it might have been something in the new water you added to the tank.
Do you dechlorinate the new tap water before adding it to the aquarium?
Water companies sometimes do work on the pipes and they usually increase the amount of chlorine/ chloramine in the water for a day after they do the work. The same thing applies if there's a sudden increase in temperature or an earthquake or disturbance that might let unwanted stuff into the water pipes. They don't normally tell you they are doing work in the area unless it's a planned outage and then they send you a letter a month before saying the water will be off on this day for x number of hours.
Other reasons the fish can die is if there is a sudden rise in water temperature. This can reduce the oxygen level in the water and the fish can suffocate. This is even more of an issue if you add carbon dioxide (
CO2) to the water because warmer water holds less oxygen and if you add
CO2 as well, you can kill the fish.
You should also check to make sure nobody has used the fish buckets for anything and you didn't have anything on your hands when you worked in the tank. Most people don't but I am just covering as many possible scenarios.
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When treating white spot, you either raise the water temperature to 30C (86F) and keep it there for 2 weeks, or at least 1 week after all the spots have gone. Or you add a medication that contains Malachite Green or Copper and keep the temperature around 24-26C. If you raise the water temperature to below 86F without adding medication, you simply speed up the parasite's lifecycle and they reproduce faster and infect the fish more heavily.
If using heat or raising the temperature to speed up the parasite's lifecycle, you should turn off the
CO2 and increase aeration/ surface turbulence to maximise the oxygen levels in the water.
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To work out the volume of water in the tank:
measure length x width x height in cm.
divide by 1000.
= volume in litres.
There are 3.785 litres in a US Gallon
There are 4.5 litres in a UK gallon
When you measure the height, measure from the top of the substrate to the top of the water level.
If you have big rocks or driftwood in the tank, remove these before measuring the height of the water level so you get a more accurate water volume.
You can use a permanent marker to draw a line on the tank at the water level and put down how many litres are in the tank at that level.
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Before you treat the tank, do the following:
Remove carbon from the filter before treating with chemicals or it will adsorb the medication and stop it working. You do not need to remove the carbon if you use salt or heat to treat fish.
Wipe the inside of the glass down with a clean fish sponge. This removes the biofilm on the glass and the biofilm will contain lots of harmful bacteria, fungus, protozoans and various other microscopic life forms.
Do a 75% water change and gravel clean the substrate. The water changes and gravel cleaning will reduce the number of disease organisms in the water and provide a cleaner environment for the fish to recover in. It also removes a lot of the gunk and this means any medication can work on treating the fish instead of being wasted killing the pathogens in the gunk.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
Clean the filter if it hasn't been done in the last 2 weeks. However, if the filter is less than 6 weeks old, do not clean it. Wash the filter materials/ media in a bucket of tank water and re-use the media. Tip the bucket of dirty water on the garden/ lawn. Cleaning the filter means less gunk and cleaner water with fewer pathogens so any medication (if needed) will work more effectively on the fish.
Increase surface turbulence/ aeration to maximise the dissolved oxygen in the water.
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