vetpath1

Thanks for the additional information (and sorry for not getting back to this for awhile). I'll try to let you know what I end up deciding in case you're interested. BTW, I just (mostly) finished my mixing station. I will be adding a drip tray below the upper container, and the RODI unit is purchased but not plumbed in yet. It's all pretty basic, with gravity feed from the freshwater to the salt. But it takes up relatively little floor space, it will be easy to add salt because the bottom container is on wheels and connected by a flexible hose, and since it will be only several feet away from the display tank (on order), I can easily use a drop-in pump and another hose to fill the tank until I get an AWC system up and running. I also don't have to maintain an external pump. The front spigot is for filling the occasional bucket with RODI water if needed. As is probably obvious, the clear tube attached to the upper container indicates the water level, which I copied from another system seen online. Happy reefing!

Thanks for the fast response! I appreciate the feedback. Yeah, I was also planning on having the display AWC waste feed the QT system and do a flow-through there too. Do you control your GHL doser with its native system, or do you use a controller? I understand that particular doser model has been discontinued. So with your doser system, don't you still have the potential for similar problems with return pump or ATO pump fails, or filter material clogs? Do you have other safeguards for those? Sorry to bug you with more questions (no good deed goes unpunished!)

I'm in the early stages of my 195 g in-wall mixed reef tank build. I'm very interested in automating my water changes, both for stability and convenience. Originally I thought I might purchase the AutoAqua system for AWC and ATO, but that product has been discontinued. I may instead have to go the Apex Dos route (I already own an Apex, but I'd have to purchase the Dos). But I have another idea for accomplishing AWC that I haven't seen posted anywhere yet, so I don't know if it's workable. I was wondering if I could drill into the return section of my sump, insert a bulkhead with an overflow drain, and then simply pump a gallon of new salt water into the display tank several times per day using my Apex or some other timer and a small pump? The water level in the return section would therefore never exceed the level of the drain, so that would essentially eliminate the possibility of flooding (unless the outflows from the display tank or sump became obstructed). I could configure the system so that the ATO (separate device) would be switched off during those auto changes. To me that approach seems simpler, less expensive, and less prone to failure than the Apex/Dos method. Seems too easy, am I missing something? Thanks in advance to all who respond.