I dont think Im wrong

Question
I have a 30 gallon tank. This is my 4th or 5th tank I've had, and it's been awhile. But I have 4 goldfish, two of witch are (baby)koi look alikes. The tank has been set up for about 31/2 weeks. Cloudy, not cloudy, cloudy, etc. Know I have fish, and they have been doing great.I feed once a day, and they finish just fine. The filter is a Tetra power 40 filter for 20-30 gallon tanks. Know my Q: is, I have one koi that acts sick some times when the others are fine. There is lots of room and plants (plastic) and rocks three air lines and a Buddha. And I also noticed what looks to be allgy  growing on one of the long plants. I've changed out the water once so far. And I've been told to declorenate the water before adding new water. Am I wrong about what I'm doing.

Answer
Hi Justin;

Your fish are okay for now but they will soon be overcrowded as they grow. Goldfish need at least ten gallons per fish because they grow to be over 8 inches long and are very messy guys. The tank is still probably breaking in too and that may be why one fish doesn't do well once in awhile. The break-in period can be very stressful to them but not all fish react to stress as strongly as others. Hopefully it will be over soon.

Water changes are best made in smaller amounts more frequently too. Change no more than 25% at a time but do them once a week. Large changes every few weeks can really shock them. Large changes can also interrupt the biological balance and cause waste toxins to accumulate.

Green Algae is not a bad thing. It's actually healthy that a tank grows algae. Just wipe it off if you don't like it. I don't recommend the use of chemical algae treatments. They can be harmful to the fish, regardless of what the product label says. Besides, your goldfish should nibbling on the algae. Goldfish are mostly vegetarian and need things like that in their diet. You can give them cooked peas, cooked green beans, squash, and romaine lettuce so they get enough fiber. It's very healthy for them.

At Your Service;
Chris Robbins