Yes, it is a cartridge filter. That's why I can't understand what the blue hose is for. Normally they put the hose on backwash filters and you don't have one. You have killed the algae (several times) now you have to remove the little dead algae bodies that can't be trapped out anymore by your already over loaded cartridge filter. It shouldn't take more than an hour (and probably much less time) to clog the filter again. This means you pull it out, blow it off with a hose, put it back, run the pump, pull it back out, wash it off with a hose put it back. You get the idea, it will plug up rather quickly and you have to keep cleaning it until all the algae is removed.