Aquarium sump questions

So I just got a 205-gallon acrylic bottom drilled fish tank for my freshwater fish. It has two 1.25 in holes on the bottom. I want to use an old 30 gallon as a sump but I have a few questions.

  1. Will using a 30-gallon sump provide enough filtration?

  2. I know the drain has to be above the water level in case of power outages to prevent overflow, but does the return line also need to be about the water, or can it be kinked like a “U”?

  3. Should I use both bottom holes as drains, then return over the top of the tank?

  4. What’s the easiest way to ensure than the drain and the pump work at the same rates?

Thanks in advance.


The holes in the bottom were intended for sealed inlet and outlet connections to the pump. I’m not sure what you intend the sump for. Is this an open air sump? In that case it has to have it’s top water level above that in the larger tank or you’ll overflow in the case of a power outage. If it’s all sealed you’ll never overflow. You shouldn’t set up something where the drain rate matters, that’s just a big wet mess or a dry pump waiting to happen. But if you must, make sure the pump rate exceeds the drain and use a valve to limit the pump rate.

Is there a rule concerning recommending other boards?
There us a tropical fish keeping board (uses the same software as the SDMB, but I digress) that would help brickbacon out.

Would you mind PMing me if need be? Thanks

What are you suggesting should be sealed? The sump top? My sump will look like the diagram on this page. They answered my question about flow rates, but I wonder if a 30-gallon sump with sections for mechanical and chemical filtration will be enough. I also am unsure whether the return valve, coming from the bottom of the tank, can be u-shaped in order to prevent backflow?

I thought a sump was filled with syphon that is short enough to run dry if an overflow begins. It seems unusual to have holes in the bottom of the tank for that.

Is your tank to be saltwater, brickbacon?

I was about to ask that, but he specified freshwater in the OP. Reef filters are open systems because they need plenty of air. But there wouldn’t be an open drain at the bottom of the tank. A bottom drain would be pumped into the sump, and then a seperate pump used at the bottom of that to fill the main tank.

It’s all a lot easier if you use an over the top siphon type drain.

I didn’t keep enough freshwater fish to be concerned with anything other than an undergravel filter. I have seen some pretty big, and crowded, freshwater tanks maintained with pretty simple filtering though.

Oops. Thanks.

Yes, with a siphon break so that it all shuts down if things go awry.

Yeah, it’s a freshwater. The tank was already drilled on the bottom, so at this point, I am just trying to figure out how to best utilize the holes. I wouldn’t be opposed to anything at this point.

I’d plug them. It sounds like a disaster waiting to happen.
Has you already been at the other forum? That was a quick post! :slight_smile:

Where did you get the tank? Perhaps it wasn’t used as an aquarium, and was drained regularly.

+1 on plugging them and use over the top plumbing, or connect your pump inlet and outlet hoses to them. You’ll have to put stop valves and disconnects in the lines so you can change the pump filter. And eventually the connections will leak, so just plug them. Use the pump output to drive an undergravel filter. Next time don’t buy a tank with holes in it. If you need a deal, find a glass tank distributor who will sell you blems. I use to get them for less than half the price of a defect free tank. Never had a problem. It’s usually just a small crescent chip on one corner that can be turned toward the wall.

Another tip about large tanks: How long are your arms? If you can’t reach the bottom, it’s too deep.

I’ve got that problem, but there are tools and stuff. :slight_smile:

I’m not fond of under gravel filters, especially in large tanks. You have to take the tank down to clean them, and they don’t work with sand. I like eco-complete as a substrate, but I can’t afford it for large tanks.

Not sure I am clear on what you are saying. Maybe I am not explain my tentative plan well. I plant to fit both bottom holes with a bulkhead with pvc piping attached on both sides. The drain hole will be a solid pipe that extends up from the bulkhead on the left hole to right below the intended water line. Thus, the only the water say, within a inch of the top, of the tank will drain down the hole via gravity. That pipe will lead down, through the tank hole into a sump located directly below. From the sump, a pump will pump the water up through the right bulkhead into the tank.

That’s where my questions arise. I wasn’t sure how the return pump should work. Does it need to be above the intended water line, or can it be fully submerged, but in a u shape to prevent backflow? During a power outage, would the water leak out of that hole in the absence of pump pressure, or would the vacuum pressure prevent that? That’s the part I am not sure about.

Hope that is more clear. Maybe I can upload a drawing to clarify.

That would help. I’m thinking that the right side would siphon out the tank during a power outage.

Sorry, I should have mentioned that you need a *reverse flow *undergravel filter. Those don’t need cleaning except for an occasional skim with a gravel vacuum cleaner (fancy name for a long hose attached to a somewhat wider piece of pipe innit?) That’s why you want to use the pump output to drive it. I think most people turn power heads 90 degrees to point down.

Somehow I thought I was specifiying reverse flow before, but I never did write it out. :confused:

Yeah, I think you want everything maintained at the same water level like in the chambered tanks in your link. No open part of the system should be below the water level or it can all drain out that way. I’m not sure what you mean by a U shape to prevent backflow. You use an air break or a back flow valve to prevent back flow.

A picture would be really nice.

Ok, here is my crude drawing. My question is, of the three options on the right, which is best to prevent drainage in case of a power outage.

Only number 3, the gray one. It has an inlet air break when the water level drops. The other two will continue draining.

What are you putting in your sump, additional filter material?


Yes, the gray lines are all above water at some point.

Three sections. One with fine filter material, one with activated carbon, and another with heaters and some course filter material. Does that sound about right?

Also, so you are saying 1 and 2 will not work, right?