have i already overcrowded my tank, and sick problems, fish species help!!!

Question
Hi i will tell you want fish i have in my 80 litre tank and could you please tell me if i have overcrowded it:1x balashark, 1x khuli loach, 1x paskistan loach, 2x clown loaches, 1x serpae tetra, 1x peacock eel, 2 x rosy barbs, 3x mollies, approx. 15 molly fry, 2x guppies, 1x black widow tetra, 2x Buenos Aires Tetra , 1x pink shirt tetra, 1x bristle nose catfish, 1x sucking catfish, 2x platys, 1x freshwater mussel and 1x opaline gourami, some of my fish keep on having sick problems, then soon pass away, it's very sad to see a fish get sick, i 've had my tank for 1 and a half years, my tank is 80 litres, i use a canister filter, i change 25% of my water every week, my PH is between 6.4 and 6.6 and i don't have a ammonia or nitrite test kit, also is their any species of freshwater gobies, what are their names and how do you take care of marbled hatchet fish?

Answer
Hi Luke;

Your tank is actually VERY overstocked. You didn't mention what size each fish is right now but even if they were all young and very small it would still be considered overstocked because of their future adult sizes. A community tank with fish that stay small (under 10 cm) can have about 2.5 cm of fish for every 4 liters of water. This means your 80 liter tank can have about 50 cm of fish safely. The combined future adult size of your fish is around 500 cm. You would need at least an 800 liter tank to keep them all. Before buying any fish it's good to research each one to determine what size they will become as adults. You can't always depend on fish store employees to tell you the facts about the fish you buy. There are some very good fish store people out there but there are far too many that are just the opposite. They may not know how big the fish will get and some will actually lie just to make the sale and get you out the door with your money in their hand. Do your own research before you buy.

There are two types of fish you have that really need another home if you aren't able to get at least a 200 liter tank right away. Your bala shark and clown loaches will each grow to be over 20 cm. They are going to start eating your mollies guppies and platies soon too, if they haven't already. Any fish can easily become a fin nipper and some downright aggressive when overcrowded. It's frustrating for them to be so close to each other all the time, not to mention the waste accumulation in there.

To keep the death and health problems down to a minimum until you can get a larger tank or find other homes for most of your fish, you should make a 25% water change three times a week and vacuum the gravel at the same time. Also get some test kits to monitor the ammonia, nitrite and nitrate levels. Make additional water changes as needed and feed the fish very lightly to slow down waste accumulation.

Below is a web page that will help you determine the future size of any fish you have or may want in the future. It also has a search utility so you can find specific fish by common name;

http://www.fishprofiles.com/profiles/default.aspx?pnl=fresh

Good luck...

At Your Service;
Chris Robbins