sick saltwater damsel!!!help he can die soon!!?

Question

i have 3 ,3stripe damsels in a 20 gallon tank with crust coral,A FISH ONLY TANK!! the tank has 2 weeks cycling,and sick damsel is 1 week sick,my reading are ammonie 1.0ppm,nitrite,3.5ppm,nitrate 0,ph 7.8, 1.023.

The first day of sick fish ,2#reading were ammonie,2.0ppm,nitrite,2.5ppm, nitrate 0, ph 7.8.
it look breathing pretty fast so i though because it WAS THE SMALLEST IN THE TANK dat maybe cuz water change, but then near his lip had a white ball, then started growing so, I DIP INTO FRESHWATER for a few secs,n then i put in a diff tank with the 2# reading of water,
but i had NO FILTER ,2 to 3 days his lip thingy went away, put kept breathing fast, n ammonie rise high of course! so today i bough a filter n small air pump, and i had to take his water off his lil tank cuz of the high ammonie,so i put the same water from the main tank. but he still breaths really fast!!maybe faster the last time. im going to dip into freshwater again, also some of my crust coral turn really green?

Answer 1

The damsel is breathing fast because of all the things you've mentioned. I'm glad to hear you were able to get a filter for it because this is how they get dissolved oxygen into the water. Marine animals are used to a fairly high amount of dissolved oxygen, and by not having a filter or airstone, the amount of oxygen present would have been low.

Right now, all your water chemistry readings (other than nitrate) are outside the ranges where they should be, and this is severely stressing your fish. Your ammonia and nitrite should be kept below 0.5 ppm - this is the levels where fish begin to get stressed from their effects. Both interfere with the ability of fish to use oxygen because it prevents the oxygen molecules from binding to receptors where it's carried by their blood. So even with the filter and airstone oxygenating the water, you fish is having a hard time breathing.

The pH of marine environments is 8.2-8.4, so at 7.8, this is low and also causing stress. Your "regular" water must not have high alkalinity and this is all the higher aragonite/shell/coral can raise it on its own.

I'd suggest doing water changes (one of about 30%, folled by whatever is necessary in the next few days) to bring the levels down to 0.5, and adding some kalkwasser to your water to raise the pH. This should help both the fish and the coraline algae. Kalkwasser comes as a powder which you add to water (I use an old soda bottle that I rinsed out well). This is very caustic, so be careful when handling - if you get any powder on you brush it off, don't rinse it - it can cause a chemical burn just as lime does. I add about a teaspoon of the powder, then fill the bottle most of the way to the top and shake a little to mix. This will make the water very cloudy, but the undissolved powder will settle to the bottom in about 30 minutes. Then use a medicine dropper or carefully pour out about a cap of the clear liquid from the top and add this to the tank.

Without knowing the tank volume or the alkalinity level of your present water, there's no way to predict how much of the kalkwasser solution you'll need to raise the pH to the correct level, but you don't want to add so much at one time that the level rises too fast and creates another problem for your fish. I would only add a capful at a time (once you've done a water change to start bringing down the ammonia and nitrite). If you have enough volume that you can change out about 5 gallons (or in multiples of 5), add a capful to a large enough bucket to mix the 5 gallons of replacement water and see what the addition of the kalkwasser does to the pH of your replacement water. If it raises it just to 8 or less, I'd add a capful per 5 gallons for now. If the pH for the first 5 gallons goes above 8, I'd only add the one capful. Since the ammonia and nitrite will need more than one water change to bring the level down to below 0.5, you can add a little more during the next water change so the amount of kalkwasser in the tank increases slowly.