Goldfish lethargic

Question
Hi,
I have a 20-25 Litre bowl with air filter, gravels and water plants and 4
smallish goldfish. Recently, I installed the air filter and discovered that the
little orang fish and the little black fish have been hanging around the bottom
of the tank near the plants away from the others. They come up to eat and
swim when touched. I've tested the PH levels and it's at 6.2 and apparently
that's fine. I also tried adding some salt which didn't seem to have much of an
effect. I also tried doing a 50% water change to no avail. I also noticed that
their fins weren't looking very healthy, they look a little ragged but i don't
think it's fin rot just yet cos it doesn't look as bad as the photos I've seen of
fin rot. I've had 2 other small nymph goldfish die in the same way already.
What's wrong with my fish and what can I do?

Answer
Hi Jo;

Your tank is just too small for goldfish. Each one needs at least 40 liters (ten gallons). Goldfish need powerful filtration too. They get big and are just very messy guys even while small. Here is a web page about them;

http://www.firsttankguide.net/goldfish.php

Change 25% of their water every day for a few days and at least twice a week after that until you can get them a larger tank.

At Your Service;
Chris Robbins