Anyhow, I've got a 46-gallon Oceanic bowfront that I've set up as a Rio Negro biotope. Water temperature is about 79F, pH 6.5, hardness almost negligible. Filtration is a Fluval 404 with a resin sponge, Purigen, and peat granules (which account for the extreme softness). Furnishings include a large, "branchy" piece of bogwood that conveniently sheds a small amount of peaty-looking "dust" on the substrate, with smaller bits and sticks scattered around the tank; the substrate is a mix of fine sand and #3 gravel, both a very light beige. Plants include one Cabomba (probably carolinia, although I'd like to replace it with aquatica and/or furcata, if they're biotope-correct), some Limnobium laevigatum floating at the top, and a few Nymphaea lotus (which I know aren't biotope-correct, but I'll explain their inclusion below). The tank is lighted by 2x55W power compact bulbs.
I set this up as a cardinal tetra/Cory biotope, so the fish population currently includes 20 cardinal tetras, 6 Otos (again, recommended by Bleher, but I don't know if they're accurate), and 6 C. robinae. I've been tempted to get a few marthae hatchets, but I think smaller tanks look better with fewer species, so I've resisted (the fact that I can't find any helps, too).
So anyhow, I have few questions. First, do the furnishings and plants sound about right for a Rio Negro biotope? The reason I included tiger lotus--with misgivings-- was that Heiko Bleher included it in his recommendations for creating a Rio Negro biotope in the first issue of Nutrafin Aquatic News. I have no idea why he included a West African plant in a Brazilian biotope, but I thought the lotus might resemble a native plant that isn't available in the aquarium trade.
Second, does the fish population sound right? Originally I had included C. schwartzi, because Bleher recommended them, but when I looked them up on FishBase I found that they weren't listed as coming from the Negro. Maybe Purus is a tributary of the Rio Negro, but I wasn't sure. I saw here on Planet Catfish that robinae comes from the upper Rio Negro, as do the cardinal tetras, so I replaced the schwartzi with the robinae. Is this tank an accurate C. robinae biotope, to anyone's knowledge?
Finally, am I in danger of overstocking? I've never been comfortable with the notion that it's OK to cram as many fish into a system as can find room to swim, just as long as there's enough filtration. (Here again, Bleher and I part ways--he recommends almost 100 fish for a 40-gallon tank! I guess they occur in very high population densities in the wild.)
Sorry for the length of this post--I tend to get a little verbose. If you've managed to read all of this extremely long post, thanks for your patience, and for any advice you care to offer.
