tank start up questions

Question
Hello, I was wondering if you could help clarify some things about tank start up.  I have a "blood parrot" cichlid who is 6 years old, and a "convict" cichlid who is about 5.I have kept them together in a small 20 gallon tank with minimal problems. I have purchased a used 35 gallon tank to give them a new home. I have had the new tank running for 7 days. ive treated the tap water with a chlorine/ammonia remover. ive added approx 8 gallons of old tank water. ive added slime coat supplement to water. I was wondering when I can safely transfer my fish to the new tank? Ive read a few different times ranging from 2 days to 1 month.
thank you soo much for your time, BRian

Answer
Hi Brian,
The main worry revolving around any new tank setup is the water quality issues that can occur soon after fish are added to it.

Even though you've added some old water from the 20 into the 35, and allowed it to sit for a week. The "good" bacteria that control ammonia are not yet established yet in sufficient numbers. And especially so since there hasn't been any ammonia food source for them to start colonizing the tank. So you must treat this tank like any un-cycled aquarium.

Stock it  slowly and gradually. Testing the water on a regular basis if possible. Which you really should do, for the sake of your parrot and convict. simple test kits for ammonia, nitrite, and nitrate helps you determine when your water is safe for your fish.

I would transfer the 20's filter into the 35's because the old filter will be full of beneficial bacteria. It may not be able to completely establish your new tank instantly, but it will help. You can move your parrot and convict into the new tank anytime now. If you move the old filter into the new tank, make sure to move the fish with them or otherwise provide an ammonia source to keep the bacteria alive. Which can be 1 small pinch of flake food added every day or so, it will decompose and provide the ammonia source.

But what I would do is transfer the filter and the fish over to the 35 gallon and be cautious of the always possible ammonia traces building up. Simply test your water for ammonia, nitrites and nitrates the day after transferring them into the tank. Do a 30-50% water change if they seem stressed (besides the usual cichlid pout behavior when they are moved) or the tests reveal climbing ammonia levels.

I hope this helps!
Karen~