Compatibility in a 38gal

Question
Nicole,

I have an established 38 gallon tank that I would like to replenish with more fish.  I have 1 Rainbow Shark, 1 opaline gourami (female), 1 chromide cichlid, 1 bolivian ram, a school of danios, an Oto, and a bamboo shrimp.  I've always been told to avoid "singles", mixing lots of individual species.  My chromide lost his buddy due to old age and seems not to care.  My beautiful Gourami enjoys her solitude (even when she had similar tank mates).  The Ram, however, is lonely.
I'd like to provide a mate for the Ram.  Are there compatibility issues that I need to be aware of?  What do you think about the balance in the tank so far?  I still need a "cleaning crew" - with this mixture, am I better off with ghost shrimp or Cory's?
Sorry for the barrage of questions, but I really appreciate the insight and guidance...
-David

Answer
Hi David,

I have not really heard the term "chromide cichlid" before, I see it is used sometimes but it is not as common. There are orange chromides (Etroplus maculatus) green chromides (Etroplus suratensis) and then there's Etroplus canarensis which is referred to as the Canara Pearlspot. Try to find out what exactly you have since their care seems to vary, going to Google.com, typing the scientific name and seeing exactly what you have. I have always been told that chromides are brackish fish but I honestly know little about them.

Opaline gouramis or Trichogaster trichopterus varies in its behavior. Females are tamer compared to the males, I had a three-spot gourami that was an absolute terror in my community tank. Traded it in for a gold gourami, again the same, if not worse. I did not try gouramis for years until I was lucky enough to find a a pair of pearl gouramis. The male is absolutely gorgeous! The female is mild, the male still nips a little at her...it seems to be fine.

If your one Bolivian ram is fairing all right then I imagine a pair will hold their own! Try to provide lots of caves so that they can retreat, and decorate heavily with plastic (or live) plants. They feel safest and look their best in a "jungle" - perhaps they will even spawn for you. It is difficult to sex Bolivian rams, especially juveniles, this article explains it:
http://www.aquariumfish.com/aquariumfish/detail.aspx?aid=9358&cid=3780&search=
"Both the dorsal extensions and the filaments of the lyre-shaped tail fin are much longer in males than in females."

Your rainbow shark might be aggressive to any of the fish commonly suggested for "cleanup" such as CAEs (ugh) and plecostomus, thankfully it seems you are only interested in corys and shrimp...I believe ghost shrimp (aka grass shrimp) would be eaten, they are after all labeled as feeders in the same vein as brine shrimp.

If you pick corys, make sure you get a hardy species that is not shy -  I don't believe say, panda corys, would do well here. Maybe you should try Brochis instead of Corydoras, the most common is Brochis splendens, go to Google.com and look up that scientific name. I believe emerald green cory is the most widely used common name.

This article gives you a rundown of keeping Brochis splendens:
http://www.aquarticles.com/articles/breeding/Kinyon_Brochis_splendens.html

Peppered corydoras or bronze corydoras might also work well, I would not keep less than half a dozen, these are awfully social fish. They also love sand as a substrate, if you don't have sand in your tank you might consider getting a little dish of silver sand or silica sand (also called pool filter sand) and putting it in the tank, just so they can nuzzle around in there. It's absolutely adorable!

I hope that helps, take care.
Nicole

P.S. Do try and get your otocinclus a couple of friends, these also are social fish and they will eat green algae.