http://www.cardinaltetras.com Cardinal tetra keeping and care information RSS 2.0 generation class http://blogs.law.harvard.edu/tech/rss http://www.cardinaltetras.com/startup-guide.php You really should have a 10 gallon or larger tank, but you can get away with something like an 8 gallon biorb or 9 gallon biube (approx 35 liters). Tetras are beautiful when they school, and this is necessary for them to show most of their colors (schooling is a defense mechanism for fish) so you want at least 6 of them. A 5 gallon tank is really pushing it, but if you were VERY diligent about the water parameters, it's possible. http://www.cardinaltetras.com/nitrogen-cycle.php This is a lot simpler than it sounds. Aquariums need to be \"cycled,\" which essentially means that bacteria in the tank are able to convert ammonia from fish waste into nitrites and then into nitrates so that the fish don\'t get sick (or die) from ammonia poisoning. This bacteria, by the way, isn\'t harmful to humans or fish; it merely feeds off ammonia and converts it into less toxic substances. http://www.cardinaltetras.com/feeding.php Tetras are omnivores, and their diet should consist of a staple flake or pellet food with an occasional treat like freeze-dried bloodworms. hhttp://www.cardinaltetras.com/cardinalvsneon.php These two somewhat similar-looking fish have some important differences. Neons are generally considered hardier, but given the pH of the tap water many people have, better luck may be found with cardinals. There is also neon tetra disease plaguging some farm-raised neons, so you have to consider that as well. In either case, make sure you buy active, healthy-looking fish, preferably ones that have been there at least a week (as opposed to delivered yesterday). http://www.cardinaltetras.com/diseases.php Noticing red or purple gills? Are your fish very close to the surface gasping for air? Ammonia poisoning is common in new aquariums that have not been cycled. A quick fix is an ammonia detoxifier like Amquel+ or Ammo-Lock (I prefer Ammo-Lock). If it\'s an emergency and you don\'t have that, do an immediate partial water change.