Join Date: Oct 2010
Location: Victoria, Australia
Plants such as duckweed help, not because they grow beneficial bacteria on their roots but because of their ability to uptake an astonishing amount of ammonia and other nutrients. It is possible to have a tank where plants act as a living filter, removing waste products and oxygenating the water. However, you need to know what you are doing to be successful with a set-up like this, and it can be a fine balance between plant growth and stocking.
Anyway, I would probably advise trying to rehome your neon tetras. They are quite a popular fish amongst the planted tank community so perhaps you could find someone who would take them.
They are quite a sensitive fish and really need a mature, established tank to do best in. If your tank isn't cycled (sounds like it isn't ) unless you are very on the ball with testing your parameters and doing water changes, you are probably going to lose them during the process.
Glofish or zebra danios, which I believe is what they are, are hardy fish. However, they are also very active swimmers and require in my opinion at least a 3 foot tank to really thrive in. I would return it and say that you were sold the incorrect fish and that you are unable to provide the adequate care for it. If the person in the fish section refuses just say you want to talk to their manager then. I'm sure they'd be happy to take back the fish rather than have to deal with the hassle of it all.
If you are keeping the neons, definitely try and get a 10 gallon tank. Also because your tank is going to start cycling whether you want it to or not, you are really going to need to purchase a test kit for ammonia and nitrite. Otherwise you will have no real idea as to what your parameters are, and whether your fish are being subjected to dangerously high levels of ammonia. Clean, clear water does not mean that it is safe for your fish, and as little as 0.5-1ppm of ammonia could be enough to kill your fish, particularly the neons.