You could go with a school of 4+ ottos. I have some in my tank, and they are great. They're apparently picky about water since they're all pretty much wild-caught, BUT I have NEVER had a problem, even when I had bronchitis with fractured ribs and pleurisy and let my tank go for three weeks (AKA: kinda crappy water).
Literally, my little ottos are a hoot. I love watching them. They're these itty-bitty little fish with these big, fat bellies (at least in my tank, I have a mini-algae farm in the planted tank, all good algae). In the wild, they school together in giant groups, so having a small school is key or they'll get stressed out and die off.
Edit: I have a cycled tank with very hard water and a seemingly high pH. I keep the tank they are in at 79*. I supplement their diet the same way I supplement my snails' diets - I throw in a weighted piece of clean lettuce for a little while and later take it out. My tank does have a filter, and it is highly planted - these fish like broad-leafed plants. You could probably wing fake plants if your tank is established with a healthy bit of algae in it. (IE: leave your light on all the time and throw in some plant fertilizer, even if you have no plants - you'll get some algae.) Otherwise, if you're leery on algae, you can throw in some algae wafers. Mine also like the flake food that the filter throws down into the plants, they eat a little bit on that, but not much. I have a low-flow tank. They did much better and were much more active when I upped the bubbles comin' outta my bubblemaker. Now they zoom in and out of the bubbles. It's truly adorable.
They're kind of plain, brown with little markings. But they're full of personality. I have regular gravel in my tank on top of a layer of ADA planting substrate - but it's pretty thick to where they wouldn't even be able to get to the finer substrate. They do just fine. I actually haven't seen them ever just suck on the gravel. They're usually all over my plants, especially the anubias. Or on the driftwood (which has a patch of teeny green algae about the size of a quarter and doesn't get bigger because they seem to eat it). (I don't mind that algae - it's the long stringy stuff that happened right after I set up my tank that scared the poo outta me, lol.) Or they're on the glass nibblin' on the algae that grows on the front and sides of the tank (small little dots, it's not really noticeable). They dance together, and have these cute little movements.
I'm a big fan, as you can tell. My girls are fine with them. And when I had them in with Ulmo, he was fine with them. And it's nice because they don't get very big. Mine are at least half a year old since I've had them, they were adults when I got 'em, and they haven't grown at all. Still about an inch in length.
The panda cories I got were about half an inch long, and my girls picked on 'em. Literally, you could see Beatrice chasin' 'em down and pickin' at 'em. Ended up pickin' a spot on one of 'em. I brought 'em back and got more ottos. BUT cories are super-cute and I'd recommend those as well.
4 Females: Muriel (VT), Beatrice (VT), Mara (VT) and Asia (VT)
7 Males: Ulmo (HM), Unnamed (DeT), Unnamed (VT), Sigmund (HM), Mizu (HM/SDT?), Jung (CT), and Paiget (??)
Last edited by Torat; 04-06-2011 at 10:19 AM.