The secret to setting up a better river aquarium

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Nathan Hill creates a useful aquatic device for those who want a river biotope tank with a more natural flow. Here's how to do it...

If we absorb the new documentaries and scientific papers we can constantly learn more and more about the biotopes our fish come from. However, one tank concept continues to elude fishkeepers — the riverine aquarium.

When purchasing rheophilic (river loving) fishes, we often tend to rely on powerful filter outlets to create suitable flows. Some keepers go further and invest in specific pumps or powerheads to bolster movement, but they end up with conflicting currents that tend to disperse at all angles within the tank.

The manifold system in the latest PFK project here is designed to ensure that water flows constantly in a straight line. It can be cranked up or down as preferred by the fish, making it ideal for any that like to cling to rocks, or dash through strong currents snatching at passing particles of food.

Some predators even find their niche in being able to outswim other fish, making use of such raging torrents in the wild to wear down their prey, before grabbing their tired meal.

In order to keep those fish with higher oxygen requirements, there’s even the option to attach a Venturi system to the pumps used. This simple feature will suck in atmospheric air through the power of water movement from the powerheads and churn out a relentless stream of fine bubbles.

What could be stocked in a tank like this? It depends one what kind of biotope you want to recreate, but most interest in river manifolds comes from the loach community. Fishes of the Balitoridae family in particular will behave just as they would in the wild, clinging on to smooth boulders and sifting through both the algae and aufwuchs — micro-organisms that live within the algae and biofilm — from the surface.

However, there’s no need to stop at loaches. Many South American loricariids, tetras and even cichlids are known to frequent rivers with colossal flow.

The very inspiration for the tank designed here was a South American river in which live various Cteniloricaria, Ancistrus and Hypostomus species. Here, they share raging waters with Astyanax tetra, tiny Characidium, Paradon and even Guianacara and Crenicichla — and just because there’s such a strong flow of water doesn’t mean that there’s no room for plants.

In the river I’ve based my design on, huge fronds of Mayaca are commonly found.

African rivers can be emulated, with cyprinids aplenty and stronger swimming Synodontis catfish. Literally, if it comes from faster waters, then this is the tank you’ll want to set up.

Be cautious about buying particularly small fish and under no circumstances place non-riverine fish into a system like this. The relentless push of water will eventually exhaust them and, given the powerful suction of the uplifted strainers, any fish that become trapped against them may struggle to break free.

This risk can be reduced by adding foam blocks over the strainers, but will still not make the tank any more suitable for slower moving fish.

Gouramis or angelfish would not enjoy this tank, so plan on setting up just for a specific target of fish species and don’t be inclined to opt for the usual community selections.

Robust décor

Substrate choice for a river tank needs to be carefully thought through. Soft, sandy substrates are prone to being pushed to one end of the tank, and planting substrates are near suicidal. Coarse sands, maybe with a softer layer beneath, are the way forward.

Decoration should be big and robust, but ideally smooth surfaced if it is to fit in with the overall image. After all, rocks that spend their lives tumbling downstream tend to be eroded over time into smoother shapes, rather than the jagged edges you’d expect to find on lava rock.

Wood and rounded cobbles should feature heavily. As well as looking authentic, these obstacles will also provide a place of quiet refuge for those fish that want to take a little time out, although quiet spots above the pumps should also serve this purpose well.

It’s vital that any décor goes in before you fill the tank with water. The plastic piping floats in water and will simply spring to the surface if all that’s holding it down is the gravel.

Alternatively, you can use a combination of suction cups and cable ties to hold the frame in place. The real diehard enthusiast can silicone the unit in permanently and allow it to dry before filling the tank with water.

Another important point to remember is not to turn the pumps off at night. When setting up a tank like this, it’s just as much for the welfare of the fish as well as for our visual enjoyment, and riverine species tend not to take a break when the lights go out.

Rivers stream 24 hours a day, seven days a week in the wilderness, and that’s what you want to recreate in the tank, too.

Be aware!

Ensure good ventilation if using the pipe cement and cleaner. The fumes of both can be harmful if breathed in.

What you’ll need

  • Enough 2.5cm/1” diameter rigid piping to span the length of your aquarium more than three times.
  • Four 2.5cm/1” 90° bends.
  • Six 2.5cm/1” tee pieces.
  • Two 2.5cm/1” caps.
  • Pipe cleaner (optional).
  • Pipe cement (optional).
  • Two powerheads.
  • Junior hacksaw.
  • File.
  • Power drill and sharp drill bit.
  • Tape measure.

Time taken

Half an hour — depending on how quickly you can clean up the cut ends with a file.

Cost at a glance

2.5cm/1” pipe at £4.40 per metre

90° bends £1.10 each

Tee pieces £1.50 each

Caps 79p each

Glue £9.98

Pipe cleaner  £10.18

Powerheads, (Rolf C Hagen Aquaclear 70s from Swallow Aquatics)

£54.99 each (all piping from ZM systems)

Total: (to set up a 90cm/35” long aquarium with strong flow) £158.82

Here's how to do it

1. I’m using a Hagen Studio 900 aquarium 94cm/37” in length. Be aware that with other aquaria there may be a central bracing bar that makes it difficult to get the finished manifold into place. In tanks with drilled bases, as with this model, you’ll need to factor this into your design.

2. Measure the lengths of pipe. I’m using three 77cm/30.3” lengths to go from end to end, allowing me space for the bends. I cut shorter, but equal sized lengths to fit between bends and tee pieces. I have a ‘dry’ run and lay my parts out so I can establish what will go where.

3. Using a level surface, I cut my piping. I ensure that they are as straight as possible to avoid inconsistencies when fitting the manifold together.

Once cut, I take care to file the swarf from the inside ends of the pipes. Any remaining may come loose and damage the pump impellers when running.

4. I clean the ends of pipes and insides of elbows, then apply a conservative amount of cement to both. Pushing the pipes into place, I hold them for ten seconds, after which they have formed a permanent seal. When cementing I need to be accurate and fast. You only get those ten seconds!

5. I cement a tee to each end of the outside lengths of pipe, ensuring they sit at the same angle. Then, using smaller pieces of pipe, I connect a tee to each corner bend. Pieces must point up 90° from the rest of the manifold, as these will house the pumps and the strainers.

6. I cement the remaining short pipes to the tee pieces and, using the two outer assemblies, ‘sandwich’ them onto the centre length. I can now focus on the uplift pipes I want to act as strainers and pump holders, so I cut lengths of pipe around 17cm/6.7” long.

7. I drill holes in two lengths before cementing on the caps. These are then connected to the tee pieces at one end of the manifold. I don’t cement them, so I can access and clean them. At the other end of the tank I insert two lengths at the height I want my pumps to sit.

8. After placing the manifold into the tank, I fit the Aquaclear powerheads using the conical adaptors provided. Once in position, I can add substrate to cover it and decorate my tank using the large, rounded stones I’d expect to find in a river. Now I just need to fill the tank!

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