I do small water changes.
25-50 gallons once a month if that.
In a system that's well over 1000 gallons
The other thing is if you let your levels get to high you'll have to clean the glass more often. lol

I change 15 gallons a week out of my 93 cube. That is a great idea! The water from that tank is near zero nitrates and pretty low phosphates.

Love it.

you've seen my arms thought right matt? i've got serious pipes a little glass cleaning won't be an issue.

Sorry meant to say my arms are like pipettes not pipes.

Hopefully the quality water from the reef tank will help keep the glass clean longer.

will running one of those hang on back filters like the fresh water ones work instead of a skimmer?

like a big aquaclear? i don't think so especially for a larger tank. those are good for some biological filtration but nothing next to a boatload of live rock. certainly not doing what a skimmer does (removes the organics from the water column completely).

Those are pretty useless on any saltwater tank. You could maybe use one to run carbon and/or some filter floss but there are better ways.