Originally Posted by Micromax
L 48x W15x D26 inches.
Posted via Mobile Device
I have used a 30g and even a 20g tank to house the fish from my 4 and 5-foot tanks. Unless you have huge fish (8-inch oscar or something) this will work. Just the tank is all you need, though it is good to have some cover, a sheet of glass or plastic, as fish will often jump under minimal stress.
The spare tank can be filled with water from the main tank, any wood or rock moved over, then the fish. Run the filter on the spare tank, it can just sit on the frame, so long as it is running with tank water, and the heater.
Drain the big tank and remove the substrate. At this point, I'm going to copy over what I wrote moments ago in another thread as it is applicable here.
Add the new substrate to the second tank. With playsand I rinse it as best as I can, dump it in the empty tank, then add about 5-6 inches of water, drain it out--this will remove a lot of fine dirt that got missed during the rinsing. Then add the hardscape (wood, rocks). Then carefully (to avoid stirring up the sand--a dish on the substrate helps) add some tap water using a dechlorinator immediately it starts to fill (to preserve the bacteria on the wood or rock if it came from an existing tank). Fill about 2/3 to 3/4 with tap water that is the same temp as the existing tank or warmer--never cooler. Move over the plants. Then move the filter and heaters over. Top up the water sufficient for the filters/heaters.
At this point I would check the pH of both tanks to ensure they are reasonably close. A difference of .5 or .6 is fine, but if it is greater, I would do a major water change in the existing tank where the fish still are, 1/2 or a bit more.
Lower the water at least half in the tank with the fish and move them over. Top up the new tank if needed. A good cover of floating plants is advisable.