Aussie_Dog
Fish Fanatic
I have two bristlenoses (along with 4 otos and a rubbernose pleco) and I think you could go with any of those. The Rubbernose might prefer over 20gals, though; knowledge about them isn't as forthcoming as knowledge of more common fish like the bristlenose and ottos. They all stay relatively small, though the rubbernose can get up to 8 inches or so. But interest-wise, I think I like the bristlenoses the best. They're always out and about, the rubbernose is always hovering around/behind/under his rock (and when he's out and about, his freaky appearance freaks me out, lol), and the ottos are so small that it's hard to figure out where they all are. The bristlenoses are just more interesting to watch, especially as they grow. One of the two is starting to grow bristles and I swear, he's getting a surge of hormones or something (he's feistier and more territorial, has grown darker-colored, and is always showing off to the other fish). The other one could be a female, or just slower developing, but he (she?) is shier than the bigger guy, and gets bossed around by him and the rubbernose (well, the rubbernose bosses everyone around, absolutely nobody is allowed to lounge on HIS rock, especially the other plecos)
Other food that you can give to the algae eaters, along with algae wafers and your own "homegrown" algae (from misc decor in other tanks, or from rocks/decor in a water-filled tub in your backyard), is fruit and veggies. I hear it's recommended to always have a steady supply of veggies in the tank, switching them out every couple of days or so. My guys go bananas for watermelon, but they love the zucchini too (someone likes to eat the green rind, but I'm not sure who it is). I put an apple slice in there last night, but it hasn't really been touched. Bananas were a so-so experiment, and they have a tendency to cloud up the water. But I've noticed that since I started putting veggies in there (especially the zucchini), the plecos have really started to grow, and it was only after adding the veggies that the one bristlenose started to grow bristles.
They also dive in when I'm serving up bloodworms or brine shrimp, and they seem to help scavenge up the tetra pellets that float to the sand. But they're mainly vegetarians so they need only a little bit of meat in their diet or they'll start to have issues.
Another note is that if you get a pleco, you'll need to get at least one bit of driftwood, as they need it for roughage. The Rubbernose adores rocks, as apparently that's where they're found with in the wild. I can attest to that as I observed the change in my rubbernose before and after I added a rock to the tank. Do research on all the algae-eating breeds/species so that you can provide the best home for it.
				
			Other food that you can give to the algae eaters, along with algae wafers and your own "homegrown" algae (from misc decor in other tanks, or from rocks/decor in a water-filled tub in your backyard), is fruit and veggies. I hear it's recommended to always have a steady supply of veggies in the tank, switching them out every couple of days or so. My guys go bananas for watermelon, but they love the zucchini too (someone likes to eat the green rind, but I'm not sure who it is). I put an apple slice in there last night, but it hasn't really been touched. Bananas were a so-so experiment, and they have a tendency to cloud up the water. But I've noticed that since I started putting veggies in there (especially the zucchini), the plecos have really started to grow, and it was only after adding the veggies that the one bristlenose started to grow bristles.
They also dive in when I'm serving up bloodworms or brine shrimp, and they seem to help scavenge up the tetra pellets that float to the sand. But they're mainly vegetarians so they need only a little bit of meat in their diet or they'll start to have issues.
Another note is that if you get a pleco, you'll need to get at least one bit of driftwood, as they need it for roughage. The Rubbernose adores rocks, as apparently that's where they're found with in the wild. I can attest to that as I observed the change in my rubbernose before and after I added a rock to the tank. Do research on all the algae-eating breeds/species so that you can provide the best home for it.
	            
 , ally86ozzy