Sump decision please help.

[nexumia]

Setup 175 bowfront.
I have a 40 gal and 20 gal laying around. Thinking about using them as sump and refugium. Not that much space underneath cabinet, but very high. If I use these already available tank then the only major cost would be a submersible pump.

OR
I can build my own sump and up it to 55gals, and use an external pump. Which I heard was better than submersibles.

Is using and external instead of submersible, and getting 15 gallons more in a sump worth, the time, money and trouble. Please advise

[Kaiser Tang]

I use a mag 12 for my return and a mag 7 for my skimmer. Both are submersed and I have never had a problem. It's much easier to just put a tank down there, drop in the pump and go. What I like most is that there are no holes to drill and no leak worries. I know that you may have some voltage in the water, but you can get a grounding rod to take care of that. If you already have those tanks why waste money in something that won't work as good or look as good.

[nexumia]

Thanks Kaiser,
Just wondering how much more beneficial the 15 gallons was.

[SandFlea]

I have read, the more water volume you have, the better off you are. If you are not planning on a refugium, or some kind of filtration in the sump, you are just going to be using the sump for extra volume anyway. You planning on doing a fuge?