Could I put a size 30 Fluval filter that is already being used in a new 40 gallon aquarium so that way the nitrogen cycle is already finished? I will it only speed it up a lot and I will only need to put in one tetra safestart that is for 20 gallons? Or should I put in 2 bottles of tetra safestart and put in the size 30 fluval filter? I just want to get the water ready for the fish to go in as soon as possible. Can the fish go in during the nitrogen cycle? Ps I will have another NEW fluval filter size 50 with the size 30 old one. Also how do you introduce the fish to the tank?