Should You Drill The Aquarium Or Use An Aquarium Overflow Box

This is a question which I get asked quite a lot. I have my own personal preference but in reality it is down to you as an aquarist to make your own decision based upon your personal preferences.

I suppose really it depends upon whether the aquarium has water in it or not.

If the [tag-tec]aquarium[/tag-tec] has water in it then you can still drill the aquarium by taking some water out so that you can drill the hole(s). There is a risk here though (as there is when you drill any aquarium with water in or not) that the glass will crack and all the water which is left in the aquarium will come crashing out and you will probably lose a lot of your fish, corals etc as well as having a soggy carpet!

That might not go down well with the other half!

You could, of course remove all of your fish, corals, rock etc to do this but lets be honest you’re probably not going to do this.

In this instance then probably an aquarium overflow box is the best for you.

If the aquarium is empty then I would definitely say that drilling the aquarium is better than using an aquarium overflow box. With the aquarium being empty you will have the option to be able to drill the holes exactly where you want them to be, the size you want as well as the number you want.

You can drill the holes in the base if you so require and configure an [tag-self]aquarium standpipe[/tag-self] type system or you can drill the rear of the tank and utilise overflows.

Another benefit is that if you drill more than one hole and one becomes blocked for whatever reason then the other hole(s) will still operate and the aquarium will not flood and the sump will not run dry.

The aquarium overflow box work normally on a siphon based system. This does have its disadvantages. The main one is that the siphon can stop. When it does the water will stop overflowing down to the sump yet the sump return pump will still be pumping water back to the display aquarium. Therefore the display aquarium may overflow and the sump will run dry probably damaging the pump.

An option to overcome this is to install more than one overflow to cope with this problem, however aquarium overflow boxes can be quite expensive therefore whilst beneficial it could end being costly in financial terms.

With both drilling an aquarium and installing an aquarium overflow box it is important to size them for the amount of water flow required. This is based upon the flow rate of the return pump(s). I would also recommend that you add extra flow to the requirements to cater for the possibility of blockage. Also remember to consider the head loss of the pump(s) when doing your calculations.

I think that you can probably see where my personal preference is – drilling. Of course an aquarium overflow box does have its advantages and if you are unable to drill the aquarium then they should not be discarded as they are a fairly easy option to install.

  1. Siphoning tubing is the most stable in the overflow box system. Problems can occur if tiny bubbles accumulate which all then becomes a huge bubble, which then you can break the siphon. This is prevented by one of two ways: BUY a stronger pump-so the tiny bubbles will get pushed through. OR use smaller diameter siphoning tubing.

  2. i agree with you that drilling is much better option than installing a overflow box due to unreliable nature of overflow boxes.

  3. I had an aquarium since 2000, recently I came home it was like 4 feets empty I had an aquarium 7and half inches by 36 (size) a lot of water all over my carpet and part in the living room, this was on a friday so I use a lot of towells and try to refill it next day as I notice no liqs, I decide to call a friend who owns a Fish store and requested to remove the aquarium for me as I was in panic this will happen again with me not been home, I never knew where the liq came from but the water spots whrere all over the wall. After reading your article I deside to write as my aquarium had if I remember well 3 diferents holes by the surface it was an acrilic tank and I will love to have another again, the corals and fish even the rocks became family to me, Iuse to clean it miself with the magnet and never change the water as I had a Dinatrator that helped a lot, never has an overflow box , if you could help me understand what happens it will be very much appreciated. Thank You Marina I live in sunny Isles Florida. Thak you for the wonderful Article……..

  4. Hello. There’s been a delay since you submitted the comment because I’ve just come back from – guess where – Florida. My wife and I were there with the grandchildren and their parents. It was great, we had a wonderful time. The temperature got to 96degF which is a lot higher than we’re used to!
    Now, your aquarium problem. The leak was clearly severe from what I can gather but I cannot give a specific cause from what you have given.
    Acrylic tanks do not have joins as glass ones do, so that’s not the cause, a leaking joint. It is possible that a pump tube came loose and the pump sent seawater out, but this would be obvious so, again, not the cause.
    You mention three holes ‘by the surface’. If seawater drained through any or all of these it would only drain to the bottom of the hole(s) and stop, so not the cause.
    One major reason for overflows is often the sump. If you had a sump maybe the pump that sent seawater back to the display tank failed, or there was a temporary power failure. In this case, seawater drains back to the sump from the display tank. This continues until the bottom of the hole where the seawater enters the display aquarium is reached when the seawater stops going down. If the hole is not positioned correctly then the seawater could drain into the sump and overflow – in other words, the sump did not have the capacity to contain all the seawater that drained down. It is important to ensure that the sump capacity is adequate when the tank is set up by turning off the pump and checking all is well. If something is to go wrong it’s often when the aquarist isn’t there!
    It would be great if you got another aquarium and came back to a great hobby. Disasters are not normal provided design is properly thought through.
    One comment I would make is that, good as equipment that aids the quality of seawater is, including skimmers and denitrators, routine seawater changes should not be entirely abandoned as they ‘freshen’ the seawater by assisting with the replenishment of trace elements etc.

  5. i was wanting a 75 gallon tank with twin overflows, i have one 75 gallon that reef ready i just dont like the place that the overflows at also i like the look of twin corner overflows so im wondering if its better to get a 75 gallon and drill my own holes or make a 75 gallon tank, also whats the percent on glass braking when u drill in a tank please eemail me or commet back if u get on como waterscape im cody9ball on their

  6. Hi. I think it’s all down to DIY skills and confidence. Some are just not too good at it and others are fully ok. For good competent DIYers making an aquarium isn’t that difficult as long as common practices are followed. It obviously needs to be watertight and the finishes need to be neat. There are other methods and materials other than glass for making aquariums but glass is the common one. Personally I’ve always bought a ready made one and modified it as required.
    Having two overflows is a good idea in case of blockage. With a ready built aquarium it’s quite easy to add overflow boxes as they are inside an already watertight aquarium. Drilling the glass is another matter as when the fittings are put in place it needs to be watertight which is usually achieved with silicone. Drilling glass is again not hard as long as patience is used and the correct drill bit, it needs to be done slowly with a correct cutter. If there is any doubt then get a local shop to drill the holes and if necessary they can silicone the fittings in place, it doesn’t cost a great deal. Any doubt, better safe then sorry.

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