Questions about building overflows and drilling a tank?
 

I have finally found homes for all of the Cichlids in my 135 gallon tank and am now ready to drain it and get it drilled and build overflow(s). The tank will be used initially as a FOWLR but I want to have the option of having enough flow if I decide to turn it into a reef tank later on. I have been doing lots of research on building overflow boxes and return lines but I still have lots of questions as I haven’t been able to find all of the answers I am looking for through web searches. What I am wondering is should I go with two overflows (1 in each corner) in a 135 gallon tank (72”L X 18”W X 24”H) or would one be enough. Also if I go with two overflows should I run a return line bulk head up through both overflows or would one be enough. I wan to keep the return line inside the tank and not have to run it up the back of the tank on the outside. Another thing I am not 100% sure about is whether or not it is ok to drill the bottom glass (is it tempered glass?) on a 135 gallon Sea Star Aquarium (the ones built in Victoria). Finally I am curious as to what size to build the overflow box or boxes (if I go with two) in the tank (the overflow box in my 90 gallon is approx. 7 ½” by 5 ½”) which gives me enough room for a Durso Standpipe and the return line.

On my 65g, I built a 8" tall by 6" wide by 4" deep. I have it drilled for a 1.5" outflow & I have my 3/4" return comes back the other side.

If I was to do it for a 6' tank, I would probably do the same for each corner, but I would have the overflow set maybe 6" from the side, so you don't see the "ugly" inside of the overflow & would have water entering from 3 sides of each overflow.

Just my experience & thoughts. There are other reefers with much more experience with overflows, so hopefully they'll chime in with their ideas too.

Have fun.

Anthony

So after doing a little more research on this I have decided that I am going to go with an 8" by 6" internal corner overflow but I am still not sure if it will be necessary to have 2 overflows to provide enough flow for a 135 gallon tank. Also I have been told that the bottom of the Sea Star tanks is drillable (non tempered glass). Can anyone confirm these ideas?

Sorry to but in here but may I ask why you decided on the internal overflows versus external? I am getting ready to build my tank and have decided on external. Just wanted to know what your reason was to go internal..

Thanks

Rich.......

I have been tossing around the idea of going with external overflows myself but after doing some research on the subject I have come up with two conclusions. External overflows can possibly fail and dump water on to the floor. Also they do not move as much gallonage as internal overflows which means you cannot run a large return pump without having to limit its flow or you risk overflowing the tank. The other reason I am not as fond of external overflows is because I want to place the tank as close to the wall as possible for aesthetic reasons. These are only the conclusion that I have come up with and I certainly do not consider myself an expert on the subject or I wouldn't have started this post.

Thanks Palster..I appreciate your comments..

Rich........

Hello,

Seastar is drillable on all panes.

If durso is 1.5" and feedline is 1" and you leave a decent space between holes for flanges and the walls of the overflow for flange space you need about 8" minimum inside overflow dimensions.

Keep in mind Sea star puts cleats on inside seams of alot of their tanks, also euro bracing.... these also influence sizes of overflows.

There is no more danger of flooding with internal vs external overflows, nor does the gallonage have to be decreased,likley it is just the opposite...instead of taking inside of tank space,youve actually added more. but yes, it will have to be placed further from the wall to accomadate them.

The best overflow possible is also the longest possible length of "spill over" with that in mind external can be done full length without taking any space at all from your reef.

Marc.

My thoughts too, and I do not have to worry about space behind as it is a built in wall tank..

Rich.....

Thanks everyone for your input. So when you say you need a minimum of 8" inside overflow dimensions is that total spill over length or do you mean the overflow has to be 8" by 8". Also are you saying that one overflow of this size would be able to handle the flow for this tank. I was thinking of using eggcrate at the top of the overflow (this is how it is done on my 90gal).

It looks as though there are a fair number of people running external overflows. It certainly would be easier than having to drill the tank. Aside from having to move the tank further from the wall I can see some advantages. I did read an article on one website where the author was claiming that when the power goes out and comes back on if the siphon for the external overflow fails to start back up when the return pump comes back on then you can have a flood.

Glenn

Outside overflow. Have a glass Co. notch the tank 2" and build your overflow boxes on the outside. You can go with the lifereef overflow boxes too but, I was talking about building your overlow boxes on the outside not inside your display. You can either notch the tank or drill holes near the top of the tank to feed the overflow boxes.

Rich.........

That explains the confusion. I was thinking of the of the siphon style overflow boxes. Those are the ones that I believe can cause flooding for the reason I had mentioned in my last post. I had never considered notching the glass and building the overflow on the outside.

Glenn

:wink:

Hello,

The total length would be your length of the overflow x1 and your depth x2.

so an 8x5 oveflow would be 18" of actual surface skimming.

But i couldnt say it would be 5" in depth because i was unsure of bracing (cleats and or euro) in your tank...the 8" is a minimum width to fit a 2 1/2" hole(1.5"bulkhead) and a 1 3/4" hole(1" bulkhead) aswell as the street 1.5" 90 that you will use on your durso, aswell as typical flange size.

You/glass company must notch the top, rather than drill holes here, holes will not work.

Marc.

Thanks Marc for all of the information. According to Reef Central's Drain Size Calculator an 18 inch overflow will handle up to 1200 gph which should be enough flow if I decide to make the tank a reef tank later on.