Advice on transferring two smaller tanks into one

[FragIt Dan]

I would either do it immediately or at any point Ammonia and Nitrite read zero ppm. If you can run some mechanical filtration to get as much of the cloudiness out of the tank it will also help, but you will be clouding the tank anyway when you move the rock over. Personally, I would move the fish into a bucket while you move the rock work over to keep the stress down but maybe drop an airstone into the bucket to aerate it.

Originally Posted by dolphinpoint

Thanks for the advice. I didn't want to use much of the old sand as I read that it can do more harm than good even if you clean it....but a cup of the old sand into the new sand should not be a problem. How long should I let the seeded new tank sit before moving the 2 tanks in along with 50 percent of the water?
Much appreciated!