Oh I'm sorry. Looking again at the OP, you describe 3 sources of flow, correct?
"So i currently have a closed loop on my 78 g system."
"I have a 2"
drain and a 1 1/2 " return split... fed by a reef flo
snapper/dart."
"Also 1 MP 40."
Probably the reason I got confused was because only 2 circulation pumps are mentioned. Out of curiosity, what pump runs the CL?
As I said above, I have moved away from CL's because of the hazards of drilled tanks. Here is my list:
1. the extra holes to be drilled
2. the extra plumbing,
3. the doubled risk of leaking bulkheads,
4. the tripled risk of the glass cracking
Why 3x risk of cracking?Between two drilled holes there is one stress line. Between 3 holes there are 3 stress lines. Add to that all the stress lines between the holes and the corners and you have quite a fragile glass box.
Plus,
for a closed loop the bulkheads are in open water, open glass. In an overflow arrangement, the holes are supported by the overflow in two ways, 1) the siliconed connection of the overflow wall with the glass surrounds the drilled holes with support and 2) a leaking bulkhead can drain only the water in the overflow, not the entire display.
Maybe it wasn't necessary for me to go into this much detail, but that's me. I like detail.
Aloha,
Mark