Help designing overflow/drilling on 65G acrylic tank

[riz94107]

I've been slowly acquiring stuff to set up my first saltwater tank - starting FOWLR, I think, but I'd like to do some coral eventually.

I picked up a nice used 65G acrylic tank (48"x15"x21") with black back panel which is currently un-drilled. I'm getting nearer to needing to make some final decisions and cutting into the tank, and could use some advice and/or suggestions.

I'm pretty sure I want a Bean Animal setup; the idea of it being self-tuning once set, and failsafe definitely appeals to me. The issue I keep coming up against is whether I should plumb the three lines to an external overflow box and have dual bulkheads through the tank into that box, or plumb directly to the tank with an internal overflow/weir. I think the reason I'm having trouble is figuring out how to attach the weir to the inside of the tank - seems like on a glass tank, I'd just silicone it in place, but I don't think silicone will hold well enough on an acrylic tank - which means, I think, using weld-on to attach it to the tank? I guess I'm nervous about my ability to do that well. (Also, not completely clear on whether it's the right path - hence this post)

Due to where I'm putting the tank and the geometry of the stand, I think the overflow needs to be on the back, either in the center or toward the left side of the tank. I _could_ do the left side instead of the back with a little finagling. I'm also open to the idea of drilling the bottom instead of the sides if I can, again, figure out the weir. Other details which might be important - the stand is limiting me to a 10 gallon sump - I've bought the tank for it (glass), and glass for the baffles, but haven't set that up yet - I've been practicing my glass cutting, and finally feel confident that I can get those right. I'm not going to have a skimmer right off the bat, but I'm planning on having one once my finances recover a bit.

I am definitely concerned with getting this bit correct - it's clearly the biggest risk for leaks, and key to making the setup look nice. It's going in my living room, so I want things hidden and quiet. Any help or suggestions gratefully accepted - thanks in advance!

 

[thegrun]

I prefer an external overflow bow, it obviously gives you more room inside the tank and there is a lot less water flow restrictions than with a large in tank overflow. Again to reduce the size in-tank overflow box I would place all three drain lines outside the tank in the external overflow box, which is what I did when I built my 120 gallon system.
That said silicone will work just fine holding an acrylic in tank overflow box in place up against the glass no matter if you use an internal or external overflow box. There isn't really that much pressure asserted onto the joint between the glass and the overflow box. Granted a silicone to acrylic joint is not strong, but for the purposes of holding an overflow box in place it will work fine.

 

[bks2100]

I'd go with something like this: http://www.bulkreefsupply.com/16-shadow-overflow-synergy-reef.html

I'd put that center in the back of the tank and drill whatever holes needed for the box I got. Then I'd drill 2 more holes at the top right corners of the back wall for returns. This way you need no silicone, nothing is glued and there's virtually zero risk of leaks. Not to mention it takes up next to no room in the tank. With the smaller water volume in the overflow area you'll have less water going into your sump when the pumps turn off. With a small sump this will be VERY important.

You could silicone in the corner but I'm not sure if I'd ever choose that unless I absolutely HAD to drill the bottom. I have that now in my tank (bought used) and it just doesn't provide any benefit. The fact that it's acrylic and silicone would seal that for me.

What's limiting you to the small sump though? I have a small sump in my 90 that holds 15g actual volume. I was screwed over by a stand that didn't have sides that open and braces in the middle. I could have had over twice the volume in my sump if it wasn't for the center brace alone.

 

[riz94107]

That box looks like just what I need - unfortunately, it's more than I paid for the tank . (Yeah, I know, I'm not in this to save money - but I'm definitely on a budget.)

That said, I'll probably wind up with something like that.

Regarding the idea of siliconing an acrylic box to the outside of an acrylic tank - would that really hold well enough to keep water in? I suppose I could test it easily-ish. Sigh - being a cheapskate generally means a lot of work.

The small sump is a function of the center brace in the stand - combining that with the narrow front-to-back just doesn't leave much room. At least I've got lots to improve for my next tank!

 

[thegrun]

I used silicone as an added protection but primarily the bulkheads I placed in the holes hold the internal and external boxes in place. Fear not!

 

[riz94107]

ok, so perhaps I've been thinking about it wrong (based primarily on some designs I've seen online) - it sounds like there are walls for the boxes (inside and outside) which go against the tank wall. And the bulkheads go through the box as well - but is there a gasket between the box wall and the tank wall (in addition to a gasket against the bulkhead flange)? If not, how does it not leak? (Maybe that's the function of the silicone?)