Purpose of holes in tank?

[luceneck]

I read a thread in the DIY section on drilling a hole in your tank, but I didn't understand why people were doing it. If I understand this correctly you can place a bulkhead and screen thing above the water level and it would take the place of a overflow. Can a hole in the tank serve any other purpose? Like a good return hole for a sump? Or can you put some external pumps on it and not need to have a powerhead in the tank?

Any help will be great!!

Luciano

[Johnnyfishkiller]

Generally people drill tanks to take the place of an overflow, You can use them for anything you like though. Usually the holes are high in the tank or in the bottom behind an internal overflow. If you put the holes low in the tank without an overflow, you risk a small leak draining the tank.

[luceneck]

So Johnny,

What your saying is that there is no need to drill a hole? I was thinking that a hole could help me take my powerheads and overflows out of the tank. Anyone else have information on this?

[mhurley]

Luciano,

Let's try this....
Do/will you have a sump below your tank?

If so, how to you get water to it from your tank and back?

Most beginners use an add-on overflow box, like this:
http://www.marinedepot.com/IMD/of_cs50.jpg

This contraption hangs on the back of your tank, the box part with the white foam is on the back side of the tank and the other (right side) is actually in the water of your tank. Water overflows from inside your tank, to the first chamber, then over to the white foamy area and then drains the water to the sump. They you attach a return line going back up hanging somewhere else in the tank.

Hang on overflows can be prone to problems because they are based on a good siphon in that little tube. If the siphon breaks, you've got a flood (because your water pump below is still pumping).

Drilling and in-tank overflows take care of this problem and get rid of that ugly box in the tank (sort of).
An overflow like this (this is an All Glass tank example looking at it from behind the tank):
http://www.all-glass.com/products/aquariums/images/megaflow_pic.jpg

There's 2 holes in the bottom of that tank. The one closest to you is the drain (bigger pipe) and the smaller back one is the return. It's not possible to lose siphon on this type of system. Water overflows the black box and fills up that chamber where the pipes are. As the water level rises to the level of the big pipe, it overflows down that pipe to your sump. They your return pump is connected to the return line. Much more elegant solution.

Now...the reason for drilling is that most beginners don't think ahead or are using second hand tanks that don't have overflows in them. So rather than go buy a new tank, they want to drill their current one and add in an overflow like pictured above.

There are different ways to do an overflow, the picture above is just one example.

Hope that helps.
Mike

[mhurley]

A couple more comments.....
Generally it's tough/impossible to drill a bottom of a tank because they tend to be tempered. You can drill an overflow in the side wall of a tank.

Also people drill holes to add a closed loop circulation system. Imagine a water pump that pulls water from one side of the tank (through a drilled hole) and returns it to the other side of the tank (through a drilled hole). The water only goest through the pump...no sump...Hence the name, closed loop, it just goes around and around. Make sense?

Mike

[luceneck]

Mike,

First of all, thank you for replying in the way you did. Pictures and illustrations always help out. Question for you: Is it possible to get that black overflow that come with the reef ready tanks? I understood the whole overflow box idea, but I didn't realize that the reef ready tanks didn't lose siphon. Would you recommend me drilling a 55 if I could find or build the black overflow barrier?

I will have a 15g sump with a skimmer/refug/ and roughly 600gph return. I didn't think of this, but If I were to have a hole in the bottom of my tank, then I would need a hole in the top of my stand!! Arghhh

[Johnnyfishkiller]

Originally posted by luceneck
So Johnny,

What your saying is that there is no need to drill a hole? I was thinking that a hole could help me take my powerheads and overflows out of the tank. Anyone else have information on this?

Do you need to drill, no. It can get overflows and powerheads out of the tank.

All I was saying is that if you drill in the bottom or low on the side of the tank, you need something to keep the tank from draining if (when) you have a leak.

The two pics that mhurly gave us show an overflow box and an internal overflow (reef ready) tank. The reef ready tank is drilled in the bottom but has internal overflows designed to both skim the surface of the water and to limit the amount of water drained out in the event of a leak.

Where you decide to drill your holes depends on your tolerance for replaceing all of your livestock when it leaks.

I'm not saying not to drill your tank. In fact I highly reccomend it. Just keep in mind murphy's law. If it's going to leak, it's going to leak when you're out of town for a week and the auto top off will keep pumping fresh water into the sump until you have hundreds of gallons of water on the carpet and a fresh water reef.

[mhurley]

Luciano,

The second picture is a reef ready tank (sorry if I misunderstood your question here).

Reef Ready tanks don't lose siphon because they don't operate on the siphon principle...They use gravity....kinda tough to lose that around here ;)

As far as drilling a 55....Be extremely careful and check with the manufacturer. If that bottom plate is tempered, it cannot be drilled. It will shatter. If the back panels are not tempered, you could drill there instead. Imagine that CPR boxed literally mounted to your back wall, instead of the water falling all the way to the bottom of the tank, it overflows and goes out the back of the tank.

You can make overflow grates pretty easy. There's nothing fancy to them. Just a sheet of plastic/acrylic with some slots cut in it, then you silicone it into place. The All-Glass models are nice because they are rounded, which is a little tougher to do. You can take 2 plates of black acrylic sheet and make a box tower in the corner.
Here's a link to a guy that makes them custom for you:
http://www.wetdryfilter.com/internal_overflow_boxes.htm


As far as your stand....I had an All-Glass 55 years ago...My All-Glass stand was not solid, it was just supported around the edges. Glass tanks don't need full top to sit on...acrylic does. So I never had an issue with working around the stand. I assume you built your own stand?

Mike

[luceneck]

Mike,

I did build the stand myself and didn't even think about the stand not being solid on top. I am actually going to get all my equipment and then consider cutting out a good size area on my stand. I will need to do it for my skimmer anyways. Switching form FW to SW has not been smooth.

I am going to look into the tempered panels on my tank. I don't think the warranty or any of the information that came with my tank will say, but a follow up with the company online will probably solve that. I appreciate your help and will do some more research before asking more stupid questions. I understand how the overflow works, I just have a hard time picturing plumbing. And when I say plumbing I mean outs, ball valves, auto top-offs, returns, and skimmers. The entire water flow system confuses me! But your replies have helped.

[mhurley]

Originally posted by luceneck
I appreciate your help and will do some more research before asking more stupid questions.

No such thing. A stupid question would have come after your tank shattered and you posted here asking why. :)
This board is great for newbies, but it can also be overwhelming because there is soooo much information and doing a search sometimes can be like plugging "aquarium" into Google and getting 2 million pages returned. Getting us to point you in the right direction is the idea.

Good luck
Mike