Adding A Sump To Freshwater Tank

I have a 20G Long tank that I've thought about adding a sump to and wanted to get some feedback.

The obvious question: Why?

These are a few of the reasons I'd like to try this.
1. Added water volume.
2. An overflow will keep my display tank's water level consistent.
3. Change the current flow in my tank.
4. A place to move other equipment: filters, heater, thermometer, etc.

The first two are pretty straightforward. I'd like to add more water volume to keep my water parameters that much more stable and it would be great to keep my water level consistent. A 20G long is rather short, so I feel like I need to keep water level right at the top, but I lose so much water to evaporation that its hard to keep it consistent.

One of the driving forces behind me wanting to change something is the water current in my tank. I currently have two HOB filters: an AquaClear 50 and a Tetra PF10. I love the ease of the AC50, but even set to its lowest flow rate, the output from the AC50 is so strong that I need to keep decorations in the return path so that it doesn't disturb the sand in my tank. The PF10 isn't as bad, as long as I keep the water level at the same height as the filter output. I had a soap dish with some marbles to baffle the flow for awhile, which worked, but I didn't care for how it looked and the suction cups kept failing and the whole thing would fall to the bottom of the tank.

So, I've been considering two sump options with both making use of a DIY overflow and a return pump. The first thought would be to simply have a bare tank below the primary tank that would house my HOB filters and heater. Would HOB filters be effective in this manner? Perhaps I could install some baffles to force water through the HOBs before being pumped back to the main tank?

The second option would be turning the sump into the filter. I've read plenty of discussion on that idea online, although this certainly intimidates me a whole lot more. I'd want to do a whole lot more homework on that before going that route.

 

This guy did pretty much what your thinking about doing. Very interesting read.

 

My 75 Gal w/ DIY Custom Stand and DIY Sump/Refugium - The Planted Tank Forum

This guy did pretty much what your thinking about doing. Very interesting read.

Thanks! That is a great read. At least I know my idea isn't too crazy, even if I plan to do it on a much smaller tank. My display tank is a 20G long and the sump will likely be a 10G.

That is a beautiful tank setup. I'm not half the carpenter that he is!

 

So, I've bit the bullet and started working on my sump.

I had planned to use my old 10G as the sump, but ultimately decided that it wouldn't fit where I needed it and I also wanted to keep it available to use as a QT. So, I've purchased a 5.5g bare tank that will serve as the sump. Small, I know, but its the largest off-the-shelf tank that will fit where I need it. I considered some plastic containers, but decided that if I'm going to install some baffles, then I'll want something more rigid. The 5.5G might be small, but since its for a 20G, I think it'll be fine.

I've also purchased some PVC and elbows for DIY overflow and I've ordered the return pump.

I've attached two different ideas for how I want to setup my sump compartments, but I know I want to have 3: intake/mechanical, biological media, and a return compartment. The trick is going to be fitting my heater into the sump with the baffles due to its length. It'll probably have to go in at an angle. I like the option on the right more, since it'll give me more space for bio media. I do have two smaller heaters I *could* use, but they're both Tetra HT10s that are preset. I'd rather have something adjustable.

Thoughts on my designs?

 

Make sure your sump has the ability to hold all water that will drain out of the main tank during a power outage. You also stated that you lost a lot of water to evaporation. Are you going to "button up" the main tank with a glass canopy? Are you going to put a Plexiglas canopy (you can cut it out for the supply & return lines and heater power cord)on the sump.

 

Make sure your sump has the ability to hold all water that will drain out of the main tank during a power outage. You also stated that you lost a lot of water to evaporation. Are you going to "button up" the main tank with a glass canopy? Are you going to put a Plexiglas canopy (you can cut it out for the supply & return lines and heater power cord)on the sump.

It may not be a lot of evaporation for some, but its enough that I feel like I need to top it off every few days to keep the water where I want it.

I know that if I let too much evaporate before filling I'll run the risk of my return pump sucking air and burning out. I will certainly run a canopy on the sump, but I'm still not sure about the main tank. I probably should. I'll see how I can incorporate a closed top into my design. I don't think I'll make it glass though, at least not entirely.

As for the risk of a power outage, yes, I'll be certain there is enough space left in the sump for the overflow and return line to drain back into the sump. I'm also thinking about an overflow switch to kill the return pump in case the overflow loses siphon or gets clogged.