Wondering if this could be done.Lets say you have 5 - 4ft tanks at the same level linked with plastic utubes connected to undergravel filters .Each intake has a filter and flows from one tank directly to the undergravel filter pushing water up thru the gravel.The very last tank has a water pump going to the first tank.Every second tank has a heater and every other tank is loaded with sand ontop of gravel and planted thick with only algae eaters like Ottocinclus and small plecos .if each tank had a valve to isolate if needed , you would have to add a temp bypass if needed.Would this work..Also if I had 4 ft by 12by 6inch tall tanks loaded say one with waterlettuce ,one with frogbite one with hyacinth and one with Crystalwort and used as a water purifier linking them together and useing this water for water changes once a week would it work .I'm planning on building a fishroom in the future and kinda thowin this out there.I'm thinking or hopein =this will work I'd like too have 2levels of 4ft tanks and the 4 pre filtertanks on top of one another plus one 4ft large below them all linked so 5 ontop of one another with a normal closed solenoid on each tank so if power goes out no floods and pump shuts off.What do you think Hope Mr. Howarth comments.