125 Gallon tank with 2 holes in the bottom of each side - The Planted Tank Forum
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post #1 of 6 (permalink) Old 04-02-2019, 04:09 PM Thread Starter
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Hey guys, really hoping to get a hand in some ideas for my 125 gallon tank that has 2 holes in the bottom of either side of the tank. (4 holes in total) first off, what are these holes for? I was leaning towards setting up a sump underneath but I am out of town for a few days at a time quite often and didn’t want to come back to a hundred plus gallon flood due to the holes at the bottom. Help? Any suggestions!? How would you suggest I set my tank up?
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post #2 of 6 (permalink) Old 04-02-2019, 04:41 PM
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Hey Avery,

Welcome to the forum from another newbie. To start, beautiful tank. What are you looking to stock?

The holes in the bottom are pretty common in reef tanks, but I am seeing more freshwater people leverage them. A sump is the easy option for using them, but many have plumbed canister filters to those bottom holes as well. Something I myself have considered doing when shopping for tanks that are predrilled.

They are also pretty easy to close. Just get some squares of glass, atleast 2" wider than the hole. Silicone the heck out of them and place the glass patches inside the tank, so the water pressures helps keep it all sealed. Once you add substrate, you'll never see them again.

With all that said, the holes are for filtration. Think about stocking and setup. Then figure out what filtration will work best.

Hope this helps.


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post #3 of 6 (permalink) Old 04-02-2019, 05:30 PM
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The holes are there for plumbing drain and return lines. Typically an overflow box would be installed inside the tank around each pair of holes with bulkheads and standpipes coming up from the holes into the overflow box. Water flows into the overflow box then through the pipes into the sump where a pump returns it to the tank.

Properly setup an overflow/sump system will provide excellent filtration without increasing the risk of a flood.

Here's a decent breakdown of the main types of overflows:
Common Aquarium Overflows - Durso, Herbie and Bean Setups | gmacreef
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post #4 of 6 (permalink) Old 04-14-2019, 01:47 AM
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Like said above it usually for reef tank or to a sump. Depend on how you are going to do your filter. Then again if you want to plug them up just do at above suggestion. I have done this before and for years and years without any problem
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post #5 of 6 (permalink) Old 04-14-2019, 02:08 AM
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I fully agree with the above thinking and it does come down to what stage you are in and where you feel you might like to go. Sealing is the way I might go as I'm not a big fan of sumps. Mostly because I've not used one and don't want the grief of doing the thought to get it right! So I might just go the easy route for the time being and change it later if/ when it felt right as silicone is an easy one to pull the patch off if you want.
But you may be ready for a sump and they do serve well for those who have done the study to get it right, so that is a good option, too.
But for ease of mind and fitting either case, big tanks or small always have some potential for leaks. Usually it is the small leak that is most common and they worry me that I might not spot one until it does real damage to the floor, etc.
So I now consider a small water alarm at every tank to just be one of the things required to insure I don't get hit with a big repair. I'm an auction site shopper and really like the small water alarms I pick up for $7. About the price of a can of fish food and gives me lots of insurance, that somebody will hear it screaming before anything major goes wrong!
Whether it is an oozing leak around a fitting for a sump or a leak from a filter, I go for the insurance.
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post #6 of 6 (permalink) Old 04-14-2019, 12:21 PM
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Something that was touched upon above - what are your thoughts on stocking? I ask this simply because in my experience if you are planning on building a nice planted tank with say 50 little cardinal tetras than a good canister filter may work nicely for you. In my case I have a 75g tank with 25+ fish in it - mostly larger rainbow fish. My over sized canister filter takes a pretty good beating and needs to be cleaned every 3 weeks.

If I were given your tank and knew I was going to re-create my heavily planted, heavily stocked situation in that tank, I would very strongly consider the sump.

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