How much flow in a river tank?

[WhistlingBadger]

Working on the design for a hillstream biotope. Tank is about 30" long, 12" deep. I want a nice, steady flow end to end.

I'm thinking about using two 200 gph powerheads (with a river tank manifold). Knocking off a bit to account for friction, that would turn over the water 15-20 times per hour. Does that sound about right?

 

[GaryE]

I like my riverine tanks!

The problem is turbulence at the end wall and in the corners. It flows back on itself and all kinds of things happen you don't want.

It sounds like a decent flow, but you'll have to see. We really underestimate flow rates - I'm a 225lb man, and I was almost knocked over by the flow in a Guatemalan stream that had mollies in it. It looked smooth, but if I had fallen, it would have swept me along for a bit. We can't exactly get close to that in a 30 inch fishtank.

 

[Archerfish]

Could you post a drawing of your idea? Turn-over rate vs flow rate are two different things. In turn-over rate, all of the water passes through the system in X amount of time. But in reality, some water will immediately return to the system while some other water will remain in eddys etc. This is an issue with filter manufacturers who claim their product will filter X GPH. They base this on a new filter, with new filter media in a sterile (tank of water no fish, plants etc.) environment. Hobbyists then try to equate that to turn-over rate per hour which is completely different. So are you asking if all of the water will pass through the powerheads or do you just want to know how much velocity the tank might encounter? Things to think about: Is the 12-inches deep the tank or water depth? Will your powerheads have filters of any kind? That will reduce their output. Is the tank bare bottom or will there be rocks and substrate? Will the powerheads be pumping the water 'uphill? Anyway, a picture or diagram will greatly help. Sounds like a really fun project!

 

[WhistlingBadger]

Water is 12" deep. Maybe a little more. Tank is 19" deep. I'm planning this as a waterfall paludarium.

I'm going to build a manifold, something like this, to move water through the tank relatively smoothly. I know the GPH figures given are approximations and ideals; as long as it's in the ballpark I doubt the fish will mind. I'd rather have too much than too little. How much turnover should I be shooting for?

 

[Archerfish]

Wow, you young guys sure can do amazing drawings! I still use stick figures!
Okay, given what I see, you will create a river flow of trout stream velocity. As GaryE said, you will have turbulence on the left side of the tank. Your fish will be pinned against the side. In my opinion you will have a trout stream until the sponges become partially restricted with debris. To answer your question the best I can, yes, you will have sufficient flow! Really, I would keep it simple and only use one powerhead and 'push' the water uphill using a hose that can be hidden on the other side (high end side). That is what I did for one of my mudskipper habitats and it worked very well. It provided a gentle, cross-tank current. Again, I think you have a really cool project!

 

[WhistlingBadger]

Thanks, but it isn't my picture. I borrowed it from here.
https://www.loaches.com/articles/river-tank-manifold-design

So, for normal hillstream species (barbs, danios, hillstream loaches, etc), maybe 20x turnover per hour is too much?

 

[threecharacters]

Thanks, but it isn't my picture. I borrowed it from here.
https://www.loaches.com/articles/river-tank-manifold-design

So, for normal hillstream species (barbs, danios, hillstream loaches, etc), maybe 20x turnover per hour is too much?

For actual hillstream species, I think 20x turnover is fine. Note, there are plenty of species of danios, barbs, etc. that don't come from swiftly flowing waters. If you can, design in an eddy or two behind rocks/driftwood where fish can rest just like they would be able to in an actual stream. You could plant the eddies too if so inclined.

 

[GaryE]

One of my friends, a technology guy, built his tank with a false bottom. The water from the powerheads (he has far better than usual laminar flow pumps) travels under the false bottom on its return. It works well, but it a lot of trouble to make. Plus laminar pumps are expensive.

Your diagram looks like the old homemade undergravel filters I used to make back in the 80s. Please don't be inspired, while making it, to get a Duran Duran haircut.

 

[WhistlingBadger]

For actual hillstream species, I think 20x turnover is fine. Note, there are plenty of species of danios, barbs, etc. that don't come from swiftly flowing waters. If you can, design in an eddy or two behind rocks/driftwood where fish can rest just like they would be able to in an actual stream. You could plant the eddies too if so inclined.

That's exactly what I had in mind! I'm going to have some river rocks, driftwood, and plants in a couple places so the different fish can kind of choose their spots, just as they would in nature.

Your diagram looks like the old homemade undergravel filters I used to make back in the 80s. Please don't be inspired, while making it, to get a Duran Duran haircut.

Oops, I already made the appointment with the local salon. Are you saying I should cancel it? Should I give away all this mousse I've been stockpiling?

 

[GaryE]

The mousse could be used to insulate cracks in the wall outside for winter.

We used to make a structure like that drawing, with pvc, only we could use a table saw to cut slashes along the pipes for a UG. They worked really well. Lost arts...

Could you kill 2 birds with 1 stone and have an undergravel as part of your stream?

 

[WhistlingBadger]

The mousse could be used to insulate cracks in the wall outside for winter.

We used to make a structure like that drawing, with pvc, only we could use a table saw to cut slashes along the pipes for a UG. They worked really well. Lost arts...

Could you kill 2 birds with 1 stone and have an undergravel as part of your stream?

No, this is going to be sort of a "super-Walstad" tank. Sponges for mechanical filtration, and emergent plants for bio. No other filter, though the waterfall pouring through a bunch of rocks will serve as sort of a de-facto undergravel filter. Except not really. But sort of.

 

[WhistlingBadger]

But seriously...how much turnover should I be shooting for? 10x/hour? 20? 13.75?

 

[GaryE]

You should shoot for as much as you can get away with. My 120, which isn't even a riverine anymore, runs at 500 gph an hour filtered, with a Hydro-Wizard rated for another possible 3000 - running at about 50% now. So I'm running at 20 times, and that's for rainbows and one leftover Steatocranus.

When I had a full colony of Steatos, before age wore the group down, I ran the HydroWizard all out. It still didn't get to the flow the rapids edge Cichlids had come from, but they liked it.

I had to raise the flow gradually so the rainbows could get into shape for it. Training... but they are very healthy bows.