Lone cichlid in a community tank?

I have a lone cichlid (the bright yellow with the black dorsal fin - not sure of the type) that is a sole survivor of a tank of cichlids gone wrong (my husband's tank). He's set up in a 10 gallon alone now with one small pleco and he's extremely happy. He has his own rock cave to protect and is happy.

However, we've developed a green algea problem that normal filtration won't remove. I've tried for weeks, changing filters, doing frequent water changes, etc. I don't want to do a drastic water change because he always acts sickly if we change out too much of his water. I'm used to the larger tank maintenance, which is always crystal clear.

I was wondering if putting him in my larger community tank would cause an issue. The small pleco I'm not worried about. The bigger tank can take another two fish, no problem. That water is crystal clear. However, I have two angels, three gouramis, and various tetras/white clouds/threadfin rainbows/neons (a few of each for color and activity). All the fish are healthy.

I know cichlids can be aggressive towards other fish. It may only be a temporary set up until I can get his tank refilled and cycled again. But I don' t want him eating my other fish! I only have one semi aggressive fish in the big tank and it's a large angelfish. I think they may have "issues" with each other.

I really don't want to add algeafix chemicals to the 10 gallon because I had a really bad experience with it before in a larger tank and I ended up emptying the tank anyway because the tank got so green. That stuff screws up the balance of the tank something terrible.

Does anyone have any experience with those fizzy tablets for algea and do you think it may help my small tank, or what do you think about putting the cichlid and pleco in my larger tank?

If I had another 10 gallon I'd already have it set up and cycling, but I don't. This was one of those things where we thought he would end up dying like the other cichlids did, but he lived - for almost 2 years now! We call him Jeff (as in Jeff Probst from Survivor) and his buddy - the ugly little pleco - is Rupert. HAHA