Anthony,
I read in your propagation book about setting up an automatic water changing system. I am finalizing the design of my sump and want to include the water changing drain. The sump will be in two sections. The skimmer section 18"L x 30"W, then three baffles to the return section (24"L x 30W). I am planning on having the baffles at 9" high so the water level in the skimmer will be 9" high, then pour over the baffles to the return. The wate level in the return section will be about 7-8" high using a top-off device. When doing water changes I am planning on changing approx 45 gallons (about 10% of my total water volume). Can you give me some insight into where I should drill the water changing drain (skimmer or return section) and how high up in the tank? The height of the tank is 17". I am guessing there is a math formula or something like that to calculate the distance up the tank to determine the amount of gallons that will be removed...but I was not very good in math.
Thanks for your help.