Inline UV would slow the filter flow some. I have not used an inline UV so I don't have a recommendation but I suspect there amy many good brands out there. Agreed, it would help with the ich issue.
Just thinking about numbers for a minute - I have an Eheim 4+ model 350 on my wifes 40g cube. Flow in the tank is decent but not huge. Would I use this filter on a 60g cube with a lot of fish - no.
If I had 2 Eheim 4+ filters on a 120g tank and a lot of fish I would also be a bit concerned. If you had room for a 3rd Eheim 4+ and used that to also power the UV then I would think you would have enough flow for "quite a few fish".
My biggest gripe with the Eheim 4+ is the top tray. When I was using one of these filters on my 75g tank I had to remove a clean the top course filter every week as it got over whelmed. As a bit of an experiment (you know I like doing experiments) I removed the top course filter pad and replaced it with Eheim ceramic MECH. Very cleanable material and less prone to getting clogged up. The bottom tray of the filter now has 2 course filter pads which actually have a larger surface area than the original small one that was at the top. Middle tray is BioMech, top tray has biomedia and a filter floss pad.
Thats my Saturday AM thoughts :-)
Thanks for checking in. I agree about the Eheim, and what I did was to buy a bucked of SeaChem Matrix, and lose all the plastic mech. I filled all the top trays with Matrix and Mech and then put a coarse filter at the bottom. I also bought Eheim pre-filters for both intakes, and they definitely are catching a lot of crud. They are easy to clean.
I donít think I have room for a third +4. Currently, the second one is plumbed through the Cerges, which necessarily dumbs down the flow. I canít find online yet what the flow wants to be through a 15 watt UV sterilizer, but generally speaking, slower is more better
so Iím thinking of plumbing a new, smaller canister through the Cerges and re-plumbing the 4+ through the UV sterilizer. Got recommendations for a decent flow canister thatís got a smaller footprint than the 4+? (And donít say Eheim Classic, because I had two 2217s that failed due to their bogus clip system!