Auto Water Change setup

[WalleyeGuy]

Ok, so I have a setup at the moment that does auto water changes on my reef tank. It has been set to change about 1.5 gal per day in total. It was set up with a Neptune DOS pump (older model that is noisy sadly) and it does the old water pull and the new water add during the same time period over about 3 hours. I was thinking though that maybe I should change it to pull all the old water first, then add the new water afterwards. Is there a particular reason why this would be a bad idea? Not sure why it was set to do both at the same time since it seems it would have less impact swapping at the same time. Thoughts?

 

[Randy Holmes-Farley]

I remove and add at the same time, which is fine even in a simple bucket. The difference is very small between that and doing them separately in time when the daily change is small. It’s a classic math problem in differential equations and the small difference is fully worked out.

I actually add downstream in the sump system from where I remove water, though that is not essential.

 

[Amstar]

agree I have my dos remove and add at the same time -- I do 1 gallon a day spread over 24 hours -- same as Randy, I pull from the one side of the sump and have the new water return at the other end of the sump near the return pump

I have a 30 gallon brute trash can with my premixed saltwater that it pulls from that goes to the sump -- and then I have the old water from the sump actually run to a drain in the floor (in the laundry room)