Can I used this pre-drilled hole for external return pump?

[SteveG_inDC]

I converted an acrylic reef-ready tank into a sump and plugged up the holes so I could use it like a box, then installed baffles to create the traditional three-chamber configuration.

However, I was wondering if i can use one of the pre-drilled holes in the back of the return chamber to run an external return pump. The thing is, the hole is about 6" off the bottom and the baffle is about 10" high. That is too close for comfort, right? Even with an ATO? I could run an elbow inside the sump so it draws water from the bottom and maybe keeps the siphon, but still -- not advisable? I don't feel like drilling new holes and honestly, there is enough room to use an internal submersible return pump. I just happen to have lying around 2 Mag 12s and one Blueline. Wondering if I just just run the two mags internal and use the blueline on my water mixing station or try to set up the blueline outside the sump. I do have plenty of room either way. Just nervous about it running dry if the return chamber water level falls.

 

[P-Dub]

With an ATO, your return chamber should never run dry or really ever change the level. Additionally, I have never had a sump run so low at to not have sufficient fluid in any chamber to keep things running. 6" above the floor of the sump is not ideal but certainly doable and with a 90 deg elbow sucking closer to the floor, it should be fine as your pump will be at the lower level outside the sump maintaining a siphon.

 

[mrk1720]

+1

With an ATO your return chamber should never run dry or really ever change level. Additionally, I have never had a sump run so low at to not have sufficient fluid in any chamber to keep things running. 6" above the floor of the sump is not ideal but certainly doable and with a 90 deg elbow sucking closer to the floor it should be fine as your pump will be at the lower level outside the sump.