Nevin's 14G + 5.5G sump

[Nevin]

Here's the back of the tank with plumbing parts:



My plan:

Herbie overflow on the left (viewed from the front, not the back as the picture above). I'll make an internal overflow from black acrylic from the top to midway down the back. Return will be on the right.

Plumbing will be as follows, from top to bottom:

Return: bulkhead, 90 elbow, union, check valve, ball valve, pump, strainer/sponge
Overflow: strainer, 90 elbow, bulkhead, 90 elbow, union, gate valve, outlet
Emergency: strainer, 90 elbow, bulkhead, 90 elbow, outlet

I will attach the plumbing to the stand so the glass doesn't bear all the weight.

I don't intend to use the return as the main source of flow in the tank, so I'm thinking of using a Mag 2 for about 200 GPH against 2' head per the Reef Central calculator vs. the Mag 3 for about 300 GPH. I don't have the experience to know what 200 GPH looks like, but I'm guessing more than that would stir up the sand too much and might be hard on the chaeto in my tiny 5.5G sump/refugium. I'll add a Koralia in the display--I have a nano and a 1.

I've never plumbed a tank before, so any advice would be greatly appreciated.