Ok Bud. I can afford one of these now. But please help me choose which one is the most appropriate. I don't see where you've listed the cubes per day ranges for each scrubber version. I have a 55ga with a 15 ga sump/refugium. perhaps 75 lbs of live rock. Right now I have 10 fish that add up to about 20 inches in total. I would like to add much more fish. I haven't yet because I have no money, no protein skimmer yet and no ATS. I never do any water changes. Not for at least a year. I have cheato in my refugium that grows like crazy. It doubles say every month and I harvest say half every month or whenever I notice it completely overrunning my sump. Some other algae also grows in the sump. But mostly cheato. I have two yellowish cfls with integrated reflectors 10" above the cheato. They come on from abut 10 am till about 11 pm every day. Haven't changed those bulbs for at least a year and a half. They are 120W each equivalent. I have just hooked up my new used Eheim 1260 as my return, and its chocked down on the output so that my overflow can handle the inflow from the Eheim 1260. For years before this I was using a small aqueon pump, perhaps 400ga.hr? as my return. At my last service I noticed that my aqueon has a broken ceramic shaft. I may have broken it when I opened it up, but it still runs seemingly normally even with the broken shaft. Planning to tee my Eheim 1260 off to feed the ATF which I plan to place above my DT to feed copepodsto the the DT. Above my sump would be nicer because it would be hidden, but if there is benefit to have it above the DT then I want to do that. I feed about 2 and a half cubes a day. Probably overfeed a bit. I have some red algae on my rocks in a few places (I'm fine with that) and my rear wall I leave uncleaned and it's a solid wall of green fuzzy algae that is perhaps 1/16 to 1/8 thick, and under that is some coraline algae. One of my fish is a scooter blenny. He seems happy enough. I don't think its fat though. My rocks have a slight yellow/green tinge to them that I am ok with. One day I would love to change my tank to perhaps a 40 breeder or a 75. Something with more than 12 inches front to back. Perhaps a 100. I would like to get a scrubber model that could handle as big a variation as possible. I understand I can adapt a specific scrubber to my system by changing things like the cleaning schedule, scrubber light periods, scrubber water-flow rate, amount of feeding, etc to control the effectiveness of a particular scrubber. Would a L3 work on my system as it comprises today? Would an L4 work? I want to grow lots of SPS in the future also. Right now I have a few easy SPS and a medium amount of LPS. My SPS is growing, but slowly. Actually I added kalkwasser as my top off about 6 months ago. It did start to speed things up. Before I was only using my RODI water to top off. I am thinking about starting to dose a little strontium, iodine, molybdenum, perhaps some other trace elements. When I did check PO4, about 6 months ago, I think it was in the 0.25 to 0.5 ppm range with Salifert, but it was extremely difficult for me to tell using that test kit. So my PO4 I think is probably still very high. My pH is 8.2 to 8.4, Ca is 475, Mg is good, dKh is 10. Ammonia is undetectable down to at least 0.02ppm. Don't know about my nitrites or my nitrates, but 6 months ago when I checked the nitrites were undetectable and the nitrates ranged from undetectable to perhaps 5 or 10 ppm over short periods of time. I should probably visit my LFS with a sample and get them to test PO4 and the nitrates for me. If I had more time I would have made this question much shorter.