Originally Posted by
Kyla
The beneficial bacteria in a tank will only grow to MATCH the bio-load in the tank. This means that as u add more fish the BB will increase in #s to consume the new, higher ammonia level being produced by the increased # of fish. So even if u add more tetras now, and the BB grows to catch up conversion of their ammonia, u still won't have enough BB in the tank to handle another future ammonia increase when u add more discus.
You have a couple choices:
1) add the discus and do large daily water changes while the BB grows to match their bioload (and test the water to make sure ur water parameters are safe during this process) - prob the most common method once the tank is already running
2) grow BB on media in a separate tank by adding ammonia directly to the water to feed the BB colony, then transfer this media to ur main tank at the same time u add the discus - or keep the discus in this tank for a quarantine/adjustment period and transfer both fish and media together to the main tank after u have used a "hero" discus to determine mixing the fish is safe - this is the safest method
3) remove all the fish from ur main tank to a separate tank with their current media. add new media to ur main tank And cycle it anew with ammonia before adding the discus.
But remember that even if u cycle a tank using ammonia (lots of info about this online) u are still just "guessing" at the bioload u are adding to a new tank. U should still test the water parameters regularly after adding fish to make sure that the # of BB in the tank is sufficient to handle the # of ammonia producing fish u have added