In the future, after I finish school and whatever, i am going to set up a North American native darter and dace tank. These are river/stream species that need high oxygen levels. Ive seen river tanks using powerheads with the intakes placed at one end of the tank using pvc and the outflow at the other, simulating the flow of a stream. But this adds clutter to the tank and added heat from the pumps which is bad.

I have seen people use wet/dry or sumps (is there a difference?) with the bulkheads placed on the bottom of the tank or at least very low on the tank. I would probably place the drains on one side and the returns on the other, but I dont really know how that works while keeping things safe from a power outage.

I dont have any experienc with this type of filtration and I just started reading about them. I understand how overflow boxes work and DIY pvc overflows but these are all at the top of the tank with no danger of more water draining than the sump can hold.

Can someone explain(digrams help a lot) how the filters work when the drains are near the bottom of the tank and do they still use overflow boxes or does the water drain straight from the tank to the sump?

ummm i wouldn't put a drain at the bottom of a tank, UNLESS it has a standpipe leading closer to the top. that's what prevents full tank drainage
as for as the return line siphoning. that's easy, a one way check valve, or a siphon break air hole (my current method)

either way it still comes down to good planning

a sump is just a water holding area and does generally help wih oxygenation because it adds surface area for the air/water interface
a wet/dry adds even more surface area due to the trickle part or the wet/dry section and is probably your best bet for oxygenation
i use a wet/dry on my tank for this reason

As Blazingwolf said you do not want to put the drains close to the bottom for a sump. You want to put the overflow or the holes towards the top of the tank. BeanAnimal is the best setup. Here is a link to some videos.

The only time I can see the holes being in bottom is if you're doing a closed loop (canister) type system but even then I would be careful. I think you're just asking for a flood. Most tanks also have tempered bottoms, which you can not drill so you would be coming off the back of the tank.

I use the same method as him to break the siphon....drill a hole in the corner of your return that will suck the air in once you lose power. This video shows how it works (towards the end)

scroll for a good diagram: here

wet/dry = place in sump where typically biomedia/bioballs are placed and water trickles over them and they are exposed to air and water. so think of a box with two grids or egg crates and in-between them bioballs . water is sprayed or injected on the top and it trickles down the bioballs and collects in the bottom reservoir where it then is pumped back to the tank. this creates an area where beneficial bacteria grow like crazy with oxygen being available all the time. hence the name wet/dry.

a sump is a plastic or glass box under the tank that has baffles to regulate the water in the sump. so you have 3 baffles, that is three chambers. assuming left to right:
1. Water Intake, this is where water enters the sump through a micron filter or sump bag
- baffle
2. 2nd chamber can be used as the wet/dry section or in saltwater where the skimmer goes, heaters and other misc stuff as well can be placed
-baffle
3. return pump chamber, this is where the return pump is placed.

That is the basic sump design, most sumps only have two chambers though, the first being combined with the second. Of course there are loads of variations to suit the application intended, for example in saltwater, a 5 or more chamber sump is not uncommon, namely, intake, skimmer section, refugium section, frag section, return pump section and ATO reservoir.

hope that helps

a drain at the bottom isn't bad, as long as it has a standpipe to take water in from higher up in the tank

right, but that defeats the purpose for which I was attempting to place the drain low in the first place. I need high flow across the whole tank including if not most importantly across the lower levels. If the drains were only up high even if the returns were low, it would likely create a lot of blowback off the side and cancel the current I was trying achieve.

Would it be safe to compromise by drilling up say 1/4 to 1/3 from bottom as to avoid a total drain, with maybe a 150 or 200 gallon tank, use something large like a 55 for a sump, and drill the sump at a safe level with a much larger hole than the drain and run a line outside or hook up to a drain if one is available in the house in case of an outtage? This might also be a good idea as I would like to run a drip system to maintain water quality and water temperature, which will have to be cooler than most tanks.

Why not use a Vortech lower in the tank and not risk it?

Wheeler that is technically an option. But if power fails and comes back on 5 minutes later and ur out at work, ull have a dead pump, a small swim area for the fish, and no water movement

Why not have the return on the bottom and the drain up high,, ull still get a current effect and on return lines u can just install a one way valve

A regular overflow suited to your need in GPH will work. Don't forget that some reefer have flow that totalize more than 20x their tank volume. Also, to be efficient, the flow threw your sump should be between 5x-10x your tank volume so that the bacteria has "time" to consume the nitrates. Maybe thinking about many powerheads pointed the right way will make it for you.

If all you're looking to do is create movement and add oxygen, I'd do a closed loop flow system similar to a reef setup. There's no chance of flood and your filtration can be set on a different system.

I dont want to use a bunch of powerheads because it will add unneccessary heat to water that needs to be cool. The fish are not tropical, not even sub tropical and the high heat levels will at the very least make for drab lookinh and unhappy fish. As far as a closed loop system I would like to but I want to run a drip system that will pump in cold water continuously at probably 1-gph, meaning a sump with a float switch or simply a drain drilled into it. Probably keep riparian veggies in the sump to help use up water and further reduce nitrates, especially if I end up having chloramines where i set the tank up.

water movement(flow) isnt the same as a current, which is what I want to achieve. Kind of like speed and velocity, you cant have the latter without direction. You may be right though and it might work just fine but I think it would work better, aka more what I have in mind, if all the holes werent near the surface. I also do not want unsightly overflow boxes in my tank, although I may build a background for a river bank feel when the time comes, which could hide equipment.

Is it possible to use diy pvc style overflows with hob overflow boxes, positioning the intakes at various depths, and allowing the siphon to break when the worst case scenario hits? Perhaps an almost coast to coast style but without the teeth and various pvc intakes instead, all of which would flow down a single pipe into the sump. Hopefully that makes sense.

This isnt going to happen for a few years at the earliest just wanna be well prepared when I can put it together.

you know what would be cool a CSD, Carlson Surge Device.

Go on....

I looked it up. Although it is cool, it would have to be like a set of 4 or 5 to keep a continuous flow, and it takes up a lot of room above the tank. It wouldnt work with a sump and drip system very well either I would think do to the flucuating water levels. If I ever decide to reef it up I will probably try one.