I ran across a post early this morning regarding having a sump on a freshwater tank and started to research what the benefits of having one are. I was planning on replacing my HOB filter soon with a canister filter and when I saw the post about the sump I thought I would look into it more. The issue I am having with making a sump is I don't quite understand how they work, at least as far as the water flow part of it goes. After searching for about 5 hours on how to build one I have not found many posts on how to build one that I can understand. If someone has experience with one I would appreciate more info on them.

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75 Gallon Planted

Well the biggest thing is that you have to have a way to let the overflow water out of the tank.
Either a hole in the bottom of the tank near the back corner.
Or a hole one the back of the tank at the level you want the water to be at
and build a box around the hole to keep the fish out of the hole.

Not every tank can be drilled.
if the tank is made from tempered glass do not drill the tank it will shatter.

I don't know how to identify tempered glass from regular glass.
The way a sump system works is this

you have a small tank about 20 gallons.
there is a divider in the tank dividing it in 1/3 and 2/3
The divider has lots of holes or slits to let water pass.
on the larger side you have the filter media (bio balls )
They have lots of little fingers and a large surface area that holds
the beneficial bacteria.
On the other side of the sump tank you have the sump area.
that has nothing but the sump pump that returns the water back to your tank.

There is a hose that comes from the tank ( the over flow hole )
and that is connected to a PVC pipe that has a T fitting and two pipes that had send caps on them and the two pipes have holes drilled in them to let the water drip over the media.
(this is also known as a drip system.)

The small side can also host your heater(s). But one additional question please. Is it possible to bypass the need to drill a tank?.. 2 "J" fixtures with required tubing feeding sump and return? Darn, that brings up another question... The pump pushing the water back to the main tank, does that insure the siphon remains intact?.. What prevents the outflow from the main to sump from effectively draining the tank and overwhelming the capacity of the sump itself? Bill in Va.

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12 Tanks, 900 gallons. Discus/Angels/Malawi/Lake Victorias. Just added a 135 & 2 - 29's..

As for not having to drill the tank goes, you can have an overflow box which gets sits at the top of the main tank and gets fed by the top part of the tank. if the tank gets to low the box "dries out" and the sump can no longer be fed preventing an overflow.
I have only been l researching this for about a day, but as I understand it as long as you have the return portion of the sump set to the proper size it would only pump out the amount of water that is in the return portion of the sump which hopefully does not hold more water than what the main tank does not contain.
Basically your overflow box prevents the sump from flooding, and the return section of the sump prevents the main tank from spilling over.
I hope that makes sense.

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75 Gallon Planted

Sorry but that won't work,
Even if you do use a valve to slow down the flow into the sump
and get it balanced with the output of the pump.
If you have a power failure you will lose the siphon prime.

And I wouldn't depend on solely on a heater in the sump.
and if the sump ever runs dry you will damage the heater.

I found this forum link that has a lot of info.
Types of Overflows, an Illustrated Guide - Marine Aquariums of South Africa

I think we posted at the exact same time.

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75 Gallon Planted

Actually KG4mxv that's not true, if you use an equalizing siphon even if you have a power outage you will not lose the siphon, if you go down a few posts and look through my thread I explain how it works (thread name is : My DIY Tank Poject (DIY Sub, Overflow Box,scenery, stand)). Also a lot of people put there heaters in there sub because it provides the most water flow over the heater, which heats the tank very efficiently and you won't have to look at it in your tank.
In the tank I'm designing I use an overflow box if your interested in seeing how that works Typeyourtexthere, so if you didn't want to drill out your tank. also you don't just have to have 3 separate sections for your filter tank, and you don't have to use bioballs, there are many different methods to making a filter tank, you can use ceramics rings, carbon, cotton, sponges, rocks, and many other different types of filter media. I recommend you look around on YouTube and on some forums there is a lot of info out there about sub systems and how to do them.

here are some links to help you



Overflows and Sumps | Reefland

The Quick and Easy Aquarium Overflow | Fish Tank Talk

You are correct, I wasn't thinking of a equalizing siphon, just a simple siphon with no vacuum break.

np, you know how long it took me to figure out how one works

If you look at a company's, any company, wet/dry filter you can figure out very easily how to build your own. Overflow box is the way to go. If the only thing you're worried about is the mechanics of moving the water in the loop, that is the easy part. As far as power failure protection goes, when the water level drop far enough the overflow stops and the return line usually has a small hole that is exposed at the same time to break the siphon of the return line. They are designed to be fool-proof.