Yes I know they are a different style of growing but we use a reservoir as well. I haven't changed my res either this grow and I think I should have. I reached into it to feel for silt and oh boy I found quite a bit of grit covering my pump, lines & bottom. I've only a week left so no point now but in the future I should do it at least once through flowering .
I almost ran my recycling pump dry by giving only 3 gal / day...every 3-4 days I had to add 6 gal just to keep the levels up over the pump.......Heat of the summer though, we're done with that now, I'll see if cooler temps have much effect on the water levels