my goldfish are floating sideways at the bottom of the tank Y

i have been having problems with ammonia levels but i finally got that under control and now this is happening. i think that one of them also has ich. i have 6 goldfish in a 30 gal. tank. i have never had any problems until 6 months ago. i have had the tank for 5 yrs. about 6 months back i lost one of my oldest fish to ammonia(i think). please can someone help me!?

Swimbladder is a disease which symptoms cause fish to become unable to swim correctly, your fish may exibit swimming toward the bottom of your tank or bowl, then floating back up, swimming in circles or laying or floating on his side..

There are three main things according to the posts and articles I've read that can lead to swimbladder disease.

Constipation due to overfeeding

Bad water quality

Bacteria

I recommend the following regimine, recommened to me over two years ago.

First, as soon as you notice signs of swimbladder do a 50% water change, taking care not to stress the fish by having the water temp as close to his tank as possible.

After your water change you should not feed your fish any food for two days. On the third day feed your fish a fresh pea. Frozen peas thawed, popped out of the skin, and cut into bite size pieces. And then do another water change so that any uneaten peas do not contaminate your water.

If you don't use aquarium salt this is a good addition to most tanks. The recommended dose is one teaspoon per gallon, or one tablespoon per five gallons. If you have never added salt and you are unsure; you may want to first acclimate him at only 1/2 tsp per gallon.