Has anyone built a river tank?


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Alberta, Canada- On the way to Ontario
5 years
So I've gotten hooked on the idea of building a river aquarium. My pygmy cories love playing in the filter flow so much I would love to build a river biotope around them and upgrade them to some sort of long low aquarium. I've seen these tanks online that have a current going all the way through but I've never seen or understood how. Has anyone done it, seen it done, done something similar, or built a river biotope before?


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3 years
I tend to use a river style configuration in most of my tanks, flow wise it's pretty easy to configure. I don't run a high speed river though. All you need to do is a) get a canister, sump, or other external filter, b) position the inlet and exhaust on opposite sides of the tank. Alternatively, you could do an in tank system like a matten filter, and run a pipe across the tank to the opposite side, I've recently done one like that and you can see it here: 29 all in one matten style corner with diy cave | 457512 | Freshwater Aquarium Builds
The top center and left tanks (10 and 20 long) on my large rack system are also river configuration, the 20 long being the fastest of them and having the more energetic species.

You can also do a really cool under gravel power head driven set up, but I haven't seen one in practice (just a YouTube video from a random fish dude, but no follow up on long term maintenance issues).

You can set up a river tank in any shape (tall vs long) tank but the consideration to be made is speed vs bio filter turn over. If you've looked into filter speed suggestions you've probably heard to turn the tank over 4-6 times. This is the balance you need to look at as it will change your water velocity. A 20 tall or a 20 long, at 5x turnover need a 100gph pump. With the same set up, the 20 long would have a much faster current than the 20 tall. Side to side the long tank would be the smaller tube so to move the same amount of water, it would have to go faster.

The spray bars to get a taller tank following proper need more attention as well. My 29 project ended up needing rows of holes in the spray bar about 120 degrees opposite eachother, with one aimed slightly up and across and the other up and towards the glass to get it going the same speed at the surface as the floor. It's my slowest velocity tank though and slow water is harder to aim than fast water. The 20 long has the most straight forward spray bar, aiming from above the surface down at about 45 degrees. I keep 1 piece of large hard scape in a place specifically to create turbulence in the flow and find many fish will sleep behind them, in my tanks it's usually a single large rock.

A note on my personal experience, I'm not keeping "serious" river species. I find silvertip tetras, harlequin rasbora and rummynose to really like it, often the clown pleco and Otto cats get into it, and endler/hybrids really could care either way. Cardinal tetras really don't seem to be fans and no matter how much I slow the tanks down and condition betta fish, I haven't gotten one to enjoy a true river. These of course are my personal observations and are limited. I do have allot of fabricating background and can design just about anything so if I were asked to crank up a tank for some hillstream or minnows I could most certainly say my experience in that facet would hold strong.

Overall notes if you are going for a fast tank, larger grain sand, or gravel are the way to go. Moon dust fine sand would be a hot mess at any real velocity. If you must run dirted, line the tank with river rock 1-3" round, then fill dirt to about 3/4 of the way up the rocks to keep the dirt from blowing out. Set up a couple current blockers to give some relaxing areas when the fish want to chill, large anchored driftwood or stones. You can fine tune your flow by drilling different spray bar patterns, then experiment with air. If you use a top draw into your filter (weir) you need a little undertow or any floating/slow sinking food will get drawn straight in at feeding time.


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Central Ohio
If you want inspiration and a little how to on building a river or hill stream tank, I recommend looking on YouTube. She has videos that show her build and rebuild of her 150gal hill stream. You may be able to use her videos figure out how you want to set up filtration, hard scape, stocking, sourcing materials, etc.

I do not have experience myself, but have seen a couple hill stream displays. You definitely want a long tank...though I don't necessarily agree with a shallow tank as part of my personal preference because I would want head space in the tank so that fish can naturally divide the tank into levels based upon where they prefer to swim. I appreciate seeing fish in the upper third in the strong current and seeing a lot of action at the bottom by bottom dwelling species.

If you have streams or creeks near you, go to them and get in the water. It will help give you inspiration for a scape and you may be able to find good sites to source scaping materials. A tip for bigger rocks: get some egg crate/light diffuser. This will be a life saver if you get some heavy stones. It will disperse the weight more evenly and allow you to have some piece of mine from fear of busting out a pane of glass from a pressure point.

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