I'm no expert, so don't assume any of this is correct...
I doubt that turnover rate would affect your ich problem. Ich is a parasite, and none of the treatments for it I have ever heard included increasing your circulation. Your filter will do nothing to rid you of ich, so the flow through the filterr specifically is certainly not going to help you.
If you have ich in your tank most of the people on this forum will tell you that you need to remove all your fish from your tank and put them into a quarentine tank. You should keep your fish in that tank for 4-6 weeks during which time the ich will go through an entire life cycle without hosts, and thus die off. If you want to medicate your fish in the QT tank there are two ways to do this...
1) Hyposalinity - You lower the salinity of the QT tank drastically, but slowly and keep it low for two weeks. This will kill ich without allowing it to burst from it's reproductive sacks, and aid in keeping as much stress off the fish as possible. This is a pretty delicate procedure according to what I read, though. If the salinity gets too high at any point (due to evaporation, most likely) you have to start all over. I'm sure you'll get some other, more educated comments and suggestions on this.
2) Copper treatment - Copper is a sure way to get rid of ich, it seems. It's lethal to just about anything that isn't a fish, though, so it only belongs in a QT tank. It also sticks in your rock and sand and slowly releases back into the water, so you definitely don't want to use it in your main tank.
The school of thought that most people follow in this forum is that ich is not always in your tank, and any
ich is a very bad thing. I don't personally buy into this theory, but the people here are more experienced that me, so some day I might. I would believe them before me.
The other school of thought not followed here is that ich is always in your tank. When you have ich attacking your fish it is due to poor water quality or just general poor health in your aquarium. Fish have a natural resistance to parasites, and stress or poor health will cause them to eventually succumb to this threat. If this is the school of thought you follow, then you should remove the infected fish into a QT tank, administer a treatment listed above, and then reintroduce them when they have recovered. During this time you should also get your water tested and address any possible issues of tank health.
Again, I've only been doing this for about six months. This is mostly hearsay, but I'm sure that most people would say I regurgitated the information fairly accurately... I can recite it in my sleep at this point.
92-gallon corner tank, 100lbs of LR
, 140lbs of sand, 250watt 10,000K MH
, 110watts of actinic PCs, Mag 7 return, custom refugium, AquaC EV180 w/ Mag 5
Female lyretail anthias, eyelash blenny, tomato clown, saddleback clown, firefish goby, 2 sand-sifting stars