There is many opinions about algae. One of the most common opinions is how horrible it is when (and if) it goes sexual.
There is no doubt that an algae going sexual will create quite an upset to the water quality. That may lead to fish losses. But there is one thing I don't totally believe about this. . .That the algae has to go sexual.
Some algae can do this (but, will it?). If the algae in question is one that can go asexual, the hobbyist who still wants to keep it has to do a couple of things.
1. Be on the lookout for when it goes sexual and take immediate action;
2. Try to prevent it from going sexual.
Few people describe what 1. looks like, but I have seen it and know what to watch for. I'll share this with you. If you are at all familiar with corn you may know that when the corn kernels/cobs are developing all the stored sugar in the plant goes into that reproduction phase. The plant turns brown. But, the plant is still alive. Its energy goes into the corn cob, from the leaves and stalk.
A similar signal is sent by macro algae before it goes sexual. The tips start turning brown AND/OR the leaves start going clear. THAT'S when the hobbyist has to intervene. Rip it out, and leave just a few stems and green leaves to restart the next generation.
As to 2. just keep it cropped. A plant that has an abundance of nutrients and gets old is prime for going sexual. Don't let it get old. I keep mine cropped back and, at the same time, watch for 1. In my own experience, after I figured out 2. I have not had my algae go sexual for over 7 years.
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What I don't care for is nori -- the human food. I prefer actual sheets of raw, chemical-free, natural macro algae. This is the first choice. Next can be actual flakes of macro algae. If grown macro algae (available sometimes on the Internet) is available and quarantined, that is an excellent choice. So is some harvested by hobbyists living in certain areas where ocean algae is unpolluted. Beyond these, Spirulina in prepared foods is great. After this, I can't think of anything.