Adding fish

Due to a low O2 problem - since corrected! - I lost my brichardi and 1 rosy barb. Have two left. The barbs at least stay out so people can see them, so they should probly stay. Will I be able to put the yellow lab back? He's in a 5g right now on emergency basis, where there is obviously not enough room for the other lab to have any territory.


25g Seavision Double Bubble 'Cichlid' (haha) Tank

2 rosy barbs (m/f)

RFUGF
Fluval3 Plus w/venturi for O2 exchange (absolutely neccessary here)
100W Visi-Therm

Crushed coral/pebbles substrate
25# assorted rock
1 small African driftwood
1 not-so-happy Java fern (getting better!)
2 large 'Second Nature' plastics

Bump?

O2 problem is about halfway down page 2 of this thread:http://www.aquariacentral.com/forums/showthread.php?s=&threadid=27013&perpage=15&pagenumber=1

If you don't wish to read the whole thing , the short answer is that changing to RFUGF almost eliminated O2 exchange at the surface due to the design of this tank (here):http://www.pet-expo.com/cgi-bin/FULLPRES.exe?PARTNUM=CE700

Ammonia 0, nitrite 0, nitrate <10ppm

Had removed juveniles calvus (to monitor his food) and 2 labs (1 calvus' buddy, other getting beaten up by brichardi) the day before and then, the stupid part, added 3 rosy barbs as 'dithers' (only a marginally larger bio-load) the day I changed over to RFUGF. Two days later, both brichardi and 1 rosy are belly-up . No signs of disease in anyone and I had had the brichardi about 6 weeks and gotten the rosies at a LFS I trust.

Now the venturi has been going about 10 days, the remaining barbs are happy, happy. So the real question is are the barbs and the lab likely to have any squabbles? I really don't want to move all the rocks again to catch a fish before it gets hurt.