I'd suggest you get atleast a 10Gallon tank. You can find a complete tank setup at petsmart for just under $40 i believe which includes heaters/filter and all that. It's a good deal because a tank and filter alone costs well over $40. But you may be talking about black neon tetra's maybe? Tetras should be kept in groups of atleast 5 but i guess 4 can manage for now. But you'll need to cycle your tank before they can live happily in there. Cycling is the growth of bacteria in oyur tank that will take care of ammonia and nitrite levels that are harmful to your fish, which will ultimately create nitrate, which CAN be harmful if it reaches high levels. If you want to keep fish in your tank while it cycles, i think you should get some danios, because they are very strong and hardy. I do not think the tetras would be able to go through the cycling process so you should try to relocate them with a friend or somewhere where the levels aren't gonna go high. Or do water changes frequently until your tank is cycled. but a 10 gallon tank is perfect for 6 shrimp, tetras, and a snail. And possibly some other fish (if you get danios, you can keep them there too). My 10 gallon has 7 neon tetras, 4 kuhli loaches, and a male guppy. It used to have 6 White cloud minnows, minus the loaches, but i removed them because they desire a colder water temperature.
To cycle.. with fish..
Setup your tank, add dechlorinated water and add heater/filter and let it run for,, lets say 30 mins, then SLOWLY introduce your fish (Danios, minnows. STRONG HARDY FISH ONLY AT THIS STAGE). To do so, just float them in a bag in the tank water for about 15 mins then get a cup full of the tank water and put it in their bag. This is important because the water parameters are different and so you need to adjust them slowly to new water. Another 15 mins later, add another cup full. If they seem fine, release them into the tank (do not put the water from there bag [fish store water] into the tank). They will produce ammonia. Soon after, there will be nitrites which is a sign of bacterial growth that consumes ammonia, making your tank safer. Soon after that, you will get nitrates, which is also a sign of bacterial growth which consumes nitrites. The process usually takes 4-6 weeks, but when i was in a rush to cycle my tank, i just bought Tetra Safe Start and my tank was fully cycled within 1 day. Beware, some people have NOT had success with that product, i did though.
Another note.. danios, minnows, tetras, etc. need to be kept in schools of atleast 5 to feel secure and happy. Some people may say that I am wrong about having so many fish in my tank, but i had well over 12 fish in my 10G tank for over 6 months, all fish healthy and no signs of aggression. The minnows and tetras actually schooled together happily:O So you can get 1-2 more of your tetras, and then keep the fish that cycle your tank (it's your preference, i used White clouds mountain minnows. They prefer colder waters than tetras though, that's why i removed them from my tank) So you still have room to add a couple more fish if you go with a 10G. or better yet, a 15G, or a 20G, etc(:
Sorry this is so long. This is all i know from my 7 months in the hobby. haha Goodluck!
Last edited by mjbn; 12-28-2010 at 12:53 PM..