I am thinking of buying the aquamedic plankton reactor with the light. I've done a lot of research and have an idea of how it works and what it needs. Having said that once I do start the system and have it running for a few days and it's ready to go, my plan is to dose my tank about every other day, and if I do that do I just replace the amount of water I took out of the system with the same amount of salt water? (for example if I dosed a cup do I add a cup of salt water to the reactor?) or do I have to wait to use up the whole thing and then restart the whole process all over?