DIY prop tank

[spineshank385]

I have a 20L, and 3 1" bulkheads along with a diamond tipped hole saw.

I would like to make a frag tank out of it.

Is there an ideal place for the bulkheads? I tried before with a 20L, with 2 bulkheads on one end, and the third on the other. The glass on the side with 2 bulkheads eventually cracked. I'm not sure whether it was because the return to the sump was unsupported, or because the tank was a little uneven, or because i tightened the bulkheads too much (hand tight + 1/4 turn with wrench), or because the bulkheads on the same pane weakened the glass too much.

Either way, i would prefer not to crack another tank. The old tank still holds water, just a slow leak, maybe 1 or 2 drops a day at most coming from the hairline fracture.

Where should i drill the holes on the new 20l?

 

[Qwiv]

You might have had the holes to close together. Holes should ideally be spaced 3x the diameter apart from eachother and sides. Milage will vary, but keep thew as far apart as you can.

 

[spineshank385]

that could have done it...they were only about 1-2x the diameter apart

 

[tripstank]

<a href=showthread.php?s=&postid=7873449#post7873449 target=_blank>Originally posted</a> by Qwiv
You might have had the holes to close together. Holes should ideally be spaced 3x the diameter apart from eachother and sides. Milage will vary, but keep thew as far apart as you can.

Huh? What? Who? I would imagine it comes down to technique and experience. Where do you get your "ideal" numbers from?

Techinically, you should be able to stack one hole over another. Use a back up board and take your time! Use plenty of water and keep the hole saw clean of chips (powder)

If you had a drill press with a low RPM, you could support the tank from underneath and use the bed of the drill inside the tank, then slowly "peck" drill the holes.

 

[spineshank385]

i know how to drill the holes, im just wondering the "ideal" location

 

[tripstank]

All the large prop tanks I have and have seen have the drain fittings at the end, the shorter leg of the rectangle with the returns on the opposing side.

You could put a small baffle in before the bulkheads to create an entire surface skimmer.

What type of frag tank? SPS, LPS, softies, mixed? The reason I ask is because of water flow needs.

 

[spineshank385]

mostly SPS in the future, hopefully, but for now some softies.

The water flow is provided by a mag 9.5, shared with my display tank. There are ball valves after the T to control water flow to both the display and the prop tank.

Before the existing tank cracked, if i opened the valve the whole way, there was MORE than enough flow for SPS. It turned the whole tank into a sideways hurricane of sorts.

 

[Qwiv]

The 3x the diameter rule has to do with the continuity of internal stresses in the plane and nothing to do with the quality of workmanship. It is a general rule of thumb and is actually very inaccurate, but doing the calculations to figure out the actual requires a computer or a hour of math I haven't done by hand in a long time. This rule obviosly does not apply if the thickness of the wall is thicker than needed, but I have to assume the tank is designed with the minimal thicknes required.