Aquael Hypermax 4500 BT external aquarium filter

The filter is controlled via Bluetooth from an app. In it you choose a constant, pulsed or wave flow pattern, and you set up a day and night mode that reduces the current when the lighting goes off. A feeding mode reduces the circulation for the duration of feeding, so that the food does not end up in the pre-filter before it has been eaten. The app also displays operating alerts and a flow graph, adjusts the lighting and the audible signals of the head unit, and a code locks the settings against accidental changes. The filter works without these settings, but on a tank of more than 1,000 litres they let you reduce the current without dismantling an outlet pipe.

For commissioning, rinse the supplied foams and any media you add in clean water, to remove the dust that would cloud the tank water. Once the tank is primed, start at a reduced setting from the app and check every fitting under the cabinet during the first hour, since it is under pressure that a poorly tightened nut starts to drip. Then increase the flow in steps until you reach the desired circulation, watching how the fish behave at each step.

The noise level ranges from 24 to 44 decibels depending on the setting. On the reduced setting, the unit stays unobtrusive in a living space; as the noise level rises with the flow rate, a tank installed in a bedroom is best run on the reduced setting at night, which the night mode does without any intervention. The tank runs on low voltage, 24 volts, and the power supply unit stays outside the cabinet. This unit therefore needs a little more space, mounted high up to stay dry, with a loop of cable below the level of the socket.

With such a volume, the amount of nitrogen produced each day is large, and that is what determines the filling. The bacteria settled in the baskets convert ammonia into nitrite, then nitrite into nitrate. In a tank that is simply planted, this nitrate builds up and is removed by water changes. In a system where crops share the fish's water, it becomes a resource instead, and it is better to keep all the baskets free for biological media rather than sacrifice one to a chemical media. The article on the nitrogen cycle in aquaponics describes these stages and the time they take on a new filter.

The 2 metre head height also allows the pump to feed a grow bed installed above a large aquarium. Placed 50 centimetres above the surface, this bed receives a sufficient share of the flow, and the water returns to the aquarium by gravity after passing through the roots. On 1,000 litres, this setup puts the nitrate produced by the baskets directly to work for your crops; the guide to building your aquaponic system describes its components.

The tank measures 55.5 centimetres high by 36 square, valves included, and it already weighs 15 kilograms empty, considerably more once full. Four castors are built into the base, so you can roll it out of the cabinet instead of lifting it. Priming is done with the piston, in a few strokes, after opening the double ball valves that keep the pipes full while you work. Measure the clearance under your tank before ordering: 56 centimetres is a minimum, and you need room to get your head in above it.

The app's graph flags the drop in flow caused by a clogged pre-filter, and this pre-filter is the part that needs cleaning most often. It comes out on its own, without opening the tank, and is rinsed in a bucket of water taken from the tank, never under the tap, since chlorine kills the bacteria. The baskets are opened only if the flow stays low after this rinse. In that case rinse just one sponge or one basket at a time, so that the media left in place seed the ones you have just cleaned. Biological media are rinsed without scrubbing, and are never replaced.