Automated Water Change.

I want to have an automated water change system for my 75g reef tank. This could be done using head pumps and a relay switch, but that would be pretty pricey.

I was thinking about using 2 aqualifter pumps and 2 timers. The timer will be used on the pump to control how long it will stay on....just long enough to remove 1.5g each day. When the first pump turns off, the next will turn on(timer), pulling water freshly mixed sw from a storage container, into my 55g sump. When the 1.5 g has been refilled, the timer will turn off the aqualifter pump.

My first worry was that my ato would mess up the salinity level big time....problem solved. Using my Aqua Controller and the PM, I will have the ato set to turn on according to a set salinity level read from a salinity probe.

What does everyone think? It sounds logical to me...

 

Water levels effect flow rates and set timers will not account for this. You will not be able to match pumps with timers. If your pumps are not matched your salinity will change.

And as a side 1.5/day is a lot for a 75g. No need to change water for the sake of changing water. I only changed 1 gallon per day on ym 90g and I thought that was too much. That is 33% per month.

 

I miscalculated a bit...so 1g a day is fine. I was trying to equal about 10% weekly.

It's a 75 plus 55g sump...total of 90g when you figure actual water volume.

 

Using a probe to control salinity is much harder than is sounds. There are all kinds of secondary consideration to account for. You need a pretty sophisticated controller to do it and the learning curve would be sort of steep. You would really need to program in a lot of security statements. Conductivity probes are not cheap either.

 

I see...what is the difference b/w conductivity and salinity probes?

 

They work and measure the same thing. Conductivity is a measure of ions and the ease or difficulty in passing a current through water. Salinity is converted from that.