The last time I tried an aquarium specific product meant to dissolve the organic waste the fish ended up gasping at the surface so I did large water changes to remove the product. Currently the O2 is at 78% saturation and I cleaned canister filter and vacuumed the sump and display tank sand. I reintroduced some bacteria (this time I used Dr. Tim's One and Only freshwater) - can I add the Septobac right away or should I wait a week or so for the other bacteria to re-establish a bit more? Ammonia and nitrite are both 0, nitrate is somewhere in the 10-15 range (I can't really tell more specifically from the colour chart). Should I expect the O2 to drop significantly after I add the Septobac (it ranges from 70-80% during the night/day)?