cloudy water after tank cleaning

Question
Hi. I have a top fin 10 gallon tank. I'm in the first year of having a fish tank. I had 3 fish in my tank. I cleaned my tank and added new gravel...I did everything I did when I got the tank the first time. Everything was fine...nearly 24hrs after tank cleaning. However, I came home tonight and the tank looked like there was smoke in it! So clouded. 2 of my fish died :( and the other fish wasn't being very active. I removed the deceased and placed the remaining guy in a sepeate bowl...I tried adjusting the thermometer...and doing a water change but nothings working. Can you help? Thank you!

Answer
Hi Kathy,

You fish most likely died of ammonia poisoning, which is the most common beginner's mistake. I'll explain why:

Fish produce waste, and the waste turns into ammonia through a natural process. Beneficial bacteria will develop in the filter and the gravel, and the bacteria converts the toxic ammonia into less harmful compounds. If you destroy the bacteria, there is not enough to process the ammonia, and ammonia reaches deadly concentrations in the tank, which kills the fish. Bacteria can be accidentally removed by:

-Cleaning the filter or changing the cartridge
-Replacing or cleaning the gravel (like you did)
-Adding a certain type of medication
-Completely stripping down the tank and cleaning it (NEVER do this!)

The smoke is bacterial bloom. This is large quantities of bacteria that have not settled in the filter yet. It will clear up very soon. (2-5 days) It could also be some dust particles.

IMPORTANT! You MUST take the remaining fish out of the bowl NOW! The chances of it surviving in a bowl are one in a million. The water volume in a bowl is much too small, and nothing can survive in a bowl. Put him back into the 10-gallon tank. Before doing this, perform a 50% water change in the 10-gallon.

The only way to ensure that the fish survives is by doing regular water changes to keep down the ammonia. I recommend a daily change of 10% a day for one week. After that, you can change 10%-20% once every week. After a month, the bacteria should be re-established and you can add more fish. Make sure you only add 1 or 2 fish at a time to let the bacteria catch up with the new load.

Next time, don't completely clean the tank or replace the gravel. If you are going to replace the gravel, put some of the old gravel in with the new gravel to encourage bacterial re-seeding.

Good Luck, and Happy Fishkeeping!