thebiggerthebetter
I hope it works out for you. I've been feeding the chlorella tabs to my 55g and 75g tanks for about four months now, and things have been running smoothly. No illness or change in behavior in the fish, beyond a dead kuhli that I am fairly certain was a victim of predation (it was gravid and slow-moving, and I found it a while later with its belly eaten). I reside in Turkey, but I believe algal supplements are a major market in the US as well. This is because of a legal loophole: if you want to sell something as medicine, you have to prove that it's at least as effective as the best existing cure for whatever you're trying to treat. But if you want to sell the same product as a supplement, you only need to prove that it's not toxic. As a consequence, many companies have turned to producing supplements that are easier to get FDA approval for.
