Molly Fish

not to be critical, but if your ammonia is that high and there's fish in the tank, then you have not been cycling the tank properly. readings that high are fatal if not taken care of immediately, and cause long term damage even if taken care of immediately.
if they are doing a fishy cycle, then 0.25 ammoina is the max ammount.

now that i think about it, it could be nitrite burn.

dont add any salt. adding any will just stress the fish by changing around the water chemistry.

what is this tank stocked with and how big is it?
 
Your fish is reacting poorly to the water conditions. You should have ammonia and nitrites sitting at 0 and your nitrates should be between 5-20. I would recommend several water changes over the next few days and keep testing the water.

Marinemom
 
if they are doing a fishy cycle, then 0.25 ammoina is the max ammount.

now that i think about it, it could be nitrite burn.

dont add any salt. adding any will just stress the fish by changing around the water chemistry.

what is this tank stocked with and how big is it?

I have to agree with your interpretation since .25 is the next reading above 0 on the test kit. To be more accurate it is between 0 and .25, but saying I had zero is wrong and anything else is just guessing. The nitrite is between .25 and .5.

The tank is a 55 and all of the inhabitants from our previous 20 gallon tank were transfered along with the water, rocks, filter media, and plants. There were 24 fish in the 20 gallon, 15 small mollys, 4 baby platys, 2 adult mollys, one small pleco, and one guppy. The fish fit fine in the 20 since they were all small except 3, but we wanted to give them more room to grow. Since setting up the 55 Gallon a couple more fish were added(mollys, swordtails, and guppys)

Only 2 of the baby black mollys have this issue, with the only other problems being a guppy that didn't like the temperature of the aquarium that has since been lowered to 78.5 and another guppy that rubs itself against the gravel every once in a while.
 
I have been cycling the tank properly (Im not a total newbie)...

He's just trying to help and no offense, but if you weren't a newbie you would know that results like ammonia 0.25ppm, nitrite: .5 ppm, nitrate: 40ppm are probably the reason why your molly is in such a bad shape and why more fish will likely follow. I wouldn't be surprised if he was exposed to much higher values in the days before. Bring the numbers down with daily water changes and put the molly in a hospital tank with proper medication if necessary.
 
The poor water quality is definitely not helping the situation.
 
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