Comments requested: 40+40 tank build!


New member
I'm moving out of state and tearing down my 37 gallon reef setup to transfer to a friend. Given this opportunity, we've decided to set up a new 40 gallon display and 40 gallon sump rig for his home, built from two 40 breeder tanks we have currently unused.

The sump design will be based on Melev's Type-F Melev's Type-F out of the bottom 40 breeder; this will be fairly straightforward.

We're now currently debating the best drilling locations for the bulkheads in the display tank. I'm 99% sure that the bottom of the 40 is not tempered glass, so the plan we're looking at now is as drawn below:


(Edited to add that this is a top view, looking down on the tank.)


  1. Are there any forseeable issues with a bottom drilled tank? Any reason to not do this?
  2. We would very much like to avoid overflows. Can the water level be controlled adequately in a setup like this through valves on the returns or intakes?

    The tank I currently have experience with is a 37 gallon that is drilled at the top with an external durso standpipe, which is not exactly a great solution in this instance for a number of reasons. The intakes in our proposed design would have strainers and would be as close to the bottom of the tank as possible.

    Since this is a new design idea for both of us, we're throwing it out to the community wisdom of ReefCentral. Any input is appreciated!

    Thanks in advance.
I was rummaging through a thread a few days ago where the whole bottom of the tank had blown out. Basically a huge spiderweb of cracks that connected all the holes he'd drilled. That's the first picture that came to mind as I read this. I suppose you'll be ok if you can support it evenly over the entire surface area of the bottom. I would stay away from any sort of trim that would raise the edges of the tank. It's the weight of the rock that made the bottom bow beyond what the weakened bottom panel could sustain that made that tank blow out. It was 1/2" too, if I remember right. The main thing to consider is that every hole creates a weak point in the glass that if bowed beyond a certain point, will just give out.
I'm interested in doing something very similar with a bottom drilled 40 gallon breeder.
Anyone else concerned with bottom drilling this tank? Would two bulkheads be less risky than 4?
Well, Catharsis70's response at least made be go back and re-read the original post, which leads me to the obvious question: How did you arrive at the 99% certainty level that the bottom of this tank isn't tempered?
Tempered glass ...

Tempered glass ...

Based on what I've read online it appears the bottom is not tempered, although if anyone has different info I'd certainly appreciate it.

Also, my 37 gallon AGA and 75 gallon AGA have tags that say "tempered glass DO NOT DRILL" on each of them. This one does not.
The All-Glass 40 breeder does NOT have a tempered bottom.
Click on Technical information.

Given this information what do you think of the bottom drilled deign? I'd like to replicate this same setup and I'm very interested in the water flow charastics/dynamics of bottom drilling a 40 gallon.

Sorry to hijack your thread, but it sounds like you and I are looking to do the exact same thing.

I'm completely new to bottom drilled tanks. If the consensus from the group is that it is too risky then I'll give up on the idea, but I don't want to eliminate the possiblity just to be safe. I understand that there is some risk involved with drilling any tank and I accept a reasonable level of risk.
I really like the idea of a hidden intake and return with no hoses sticking out from the back of the tank. I want to sit this setup as close to the wall as possbile.

Who out there has successfully bottom drilled their tank? How would you alter the design of your bulkheads if you had it to do over again?
I was rummaging around trying to find that thread, but no go.

If I can summarize what I remember of it, the bottom was 1/2" untempered. A DIY tank start to finish, big tank, I want to say 300G. Six holes @1 1/2 inch for much the same as you're trying to achieve. The glass had flexed enough from the water pressure and rock that it just looked like a big old spider web connecting all the bulkheads. I believe there was some "hindsight" offered in the thread about having the bottom tempered after it was drilled. I'm a big fan of DIY, but if I can ever throw out meaningful words of caution, I will. And that's all I'm trying to do here.

I think most will agree that holes in a glass panel create weak points from which a crack can develop when the panel is flexed sufficiently. What I certainly can't do is quantify that statement by saying how many holes is too many. There have been suggestions about how far holes should be from an edge, which I think is the equivelant of the hole's diameter, but hopefully someone will check me on that.
use a calfo manifold return. the less holes you drill in the glass the better, especially on the bottom where your rock and sand will be adding all the pressure. or you could just drill 1 drain and return. i really would advise against having your strainers on the intakes close to the bottom. if you have a power failure, your whole tank will drain and flood your sump.
The intakes in our proposed design would have strainers and would be as close to the bottom of the tank as possible.

IMO not a good idea, several reasons.
Film will build up on surface hindering light PAR.
Accident waiting to happen if and when something knocks into it (rock COULD fall)
If t leaks or busts, I'd rather have 1/4 my water stay in the tank to maybe save some life, rather than the whole thing empty.

Wether you drill the botom, the back, or the side, you still need to extract water from the surface using either an overflow or standpipe. So I'd just drill the back to be safe.
Excellant points on the returns. I agree. I was so focused on teh # of holes in a non-tempered bottom, I missed that.