Emludwig

My Goldie has been just laying on the bottom for a few days. The other 4 goldies are fine. They are not the buggy eyed kind. They're smaller and regular looking. They have all been living together for about 6 months. They were in an algae infested tank for months until about a month ago when we got them a new 20 gl tank with filter. For the first 3 weeks all was fine. Now the big fish just lays at the bottom. When I feed them flakes they all eat. But after that he goes back to same spot and just lays there. We have well water so there are no chemicals in it. We test it for bacteria and nitrates quarterly and always there is none. The water is hard and has high pH but it's the same water they've always lived in.

Help!!

gremlin

Since it is a fairly new tank set up, and you have 5 goldfish in a 20 gallon tank, it could be ammonia build up. Test the water for ammonia, nitrite, and nitrate. See if you can find a good liquid test kit since the test strips tend to be wrong. The general rule of thumb for goldfish stocking is 20 gallons for the first goldfish with an additional 10 gallons for each additional goldfish. Since the four "smaller and regular looking" goldies are probably common or comet goldies, they will need even more room for swimming. Your five goldies should really be in about a 75 gallon tank. Your tank is probably not fully cycled so there is ammonia in the water that is affecting your fish. The fancy "bug eyed" goldie is probably showing signs of ammonia poisoning. I would suggest daily 50% water changes with Prime or Ammo-Lock (or a similar water conditioner that will neutralize the ammonia) and test daily until your tank cycles.

Emludwig

Oh and his right eye is a little cloudy/filmy if that makes a difference. All the other fish are fine. How does amonia get in there?

aquarist48

Hello Emludwig and Welcome To Fish Lore.

Below is a link to help you to understand the nitrogen cycle which is crucial to fish keeping. If you have questions by all means let us know. We're here to help.
The Aquarium Nitrogen Cycle

Ammonia comes form fish waste and decomposing fish food.

Having your own test kit is very important to the hobby. One that is most recommended is the API (liquid, not test strips) Master Test Kit. It will test for everything mentioned in the Nitrogen Cycle link I posted above.

Gremlin has given great advice about the daily water changes and adding a water conditioner called Prime (Amquel + works great too). This will help to keep your fish safe until your tank has cycled. It's going to take some effort on your part right now, but it will get easier once your tank has cycled.

Best wishes,
Ken