Hello fellow aquatic enthusiasts! I purchased this RO/DI system from a fellow aquarist on the forums 5 years ago and have now been able to hook it straight to my water system. The system had water sitting in it for the past year without being used. I have hooked it up and discarded of the first 5 gallons it produced. I would like to change the filters but do not know where to look for replacement filters. The input and output are 1/4" lines so I assume it is a 50 gpd unit but do not know for sure. What are the 2 additional tanks on top of the unit? I am assuming one is the membrane. Is one an inline carbon filter and what is the 3rd? I do still get 0ppm hardness so it doesn't seem the membrane is compromised. Can I use generic filters off amazon for replacement? Thanks for any help you can provide!