Weird Saltwater Keeper

Hi all! I've lurked around here for a while, and your experience has really helped me maintain my tank and keep my fish happy and healthy! I've kept aquariums since I was very little, but didn't ever set up a real salt tank until I moved into my college's dorm this year. It's been kind of a wild time figuring out all of the appropriate care for my tank, but I've stuck with it, and I'm now the proud curator of a Porc and a Jeweled moray! They're both really young, and are definitely growing fast. I have them in a 20gal FOWLR right now, which is basically just a long-term QT until I can move them into something like a 100gal or larger, back home. I'm totally aware that this is unacceptable for these fish long-term, so I've saved some money to upgrade them when I'm firmly rooted back home, 'cause there's no chance of getting a 100gal into a residence hall unnoticed.:funny: I have a small hair algae problem, and a classic side-of-the-tank algae problem as well, and I was wondering if anyone knew of anything that would effectively remove/control them long-term? I'm not actually interested in killing the hair algae for now, it's one of the few planted things that can survive with the pitiful 18w bulb I've got in there right now. My puffer goes after anything that moves, especially inverts, but also small fish, up to an inch or two in size. He cleared out about 10-12 Mollies I put in as vacation food in about 2 weeks. He's well adjusted to eel tankmates, but his previous Snowflake bro jumped ship through the filter outflow, which is now firmly taped to the tank. Any inverts that could survive a Porc attack? Small left-handed hermits seem to be safe, as are some kind of Cerith cone shell snail that eats the biofilms and not the algae. He eats Nassarius, Nerites and Urchins as well, can confirm. I think he got an Astaria Turban Snail once too. The algae grows too slowly for turbo snails, and my Porc figured out that the lettuce sea slug I tried (I know they only temporarily help, but it was super cute) in about half a second and minced him. I'm kind of running out of options, and it doesn't help that I can't upgrade them yet and just throw a wrasse or cleaner fish in there. Honestly, if there was a magical saltwater pleco, that'd be what I want. On another note, does anyone have experience with Hydrazoans? I've got a colony/plague of small white Hydras that won't go away. I can post up pictures if anyone is interested, because I've never seen anything like them outside of biology lectures on freshwater cnidarians. They don't seem to make medusa stages either, but they may do it when I'm not watching. Water parameters are nominal, Ph around 8.1, Nitrates and Ammonia a flat 0, and Nitrates that waver between low(<20ppm) and red-lining high(higher than my test kit can give results for) after feedings. It may be the food I use, which is exclusively clams on the half-shell, atlantic cod from the grocery store (the only thing my jeweled moray will eat are fish/krill) and frozen peas/lima beans for Porky, all teated with garlic powder and sometimes cane sugar for flavor. I used to feed them whole silversides. I'm sorry that this is a sort of dump post, and I'll probably chop it up into the relevant threads later, but if anyone happens to know about these issues, I'd love any opinion.