Fish Tank Safe Flow Meter

Someone asked me if I could design an Arduino based system to measure the flow rate of a water pump in a fish tank.

I have zero experience with any kind of fish tank. I would imagine a flow sensor would just go inline with the output of the pump, which is easy enough. But, some questions arise...

Is there a standard size hose that would be compatible with a sensor?

Is there a particular type of sensor that is better suited for the "fish" environment? I know some species are very "delicate" when it comes to, well, anything (had a friend lose an entire tank in under 12 hours once because something foreign was introduced- I don't want to be in that boat).

Water is a nasty environment... do these things get clogged or have to be cleaned occasionally? Last thing I would want is a clogged flow sensor blocking the output of the pump.

Is there a sensor that is more "industrial" that will work with Arduino? The ones I'm seeing are all part of experimenter kits and look pretty flimsy. For a prototype or proof of concept they look fine, but for something that has to perform for months or years at a time...


There are several pass through flow sensors I'd use for such a project that I found on Amazon.

Fresh or salt water?

I would seek to know about algae control. I'd want the recirculating water fed from the filter/pump, in darkened tubing, from the pump/filter into the flow sensor.

If there is not any algae control, I'd not do the project cause the flow control unit will get clogged in a very very short time.

There is a standard tubing sizing scheme, you'd need to examine the tubes or piping that is being used on the pump output.

Is the filter pump an outside filter or a canister filter? Tube sizing.

Get a small fish tank, buy some guppies and use them as your test subjects. It should take about 21 days for the flow meter and associated piping to get enough microbe build up to use in the real tank. If the tank that you want the flow measured is an established tank, then 'everything' is coated with a balanced microbiome. If you put clean units into the water flow, such as a flow sensor and piping, the microbiome will bloom. The bloom will kill the fish. You'd want to use some water from the tank target in your adjustment tank to speed up the formation of a microbiome.

Is there a fluidized bed filter, as part of the filtering system, in use?

Is there a outside tank filter in use that has a layer of nicely browned ceramic?

You got to keep in mind that when you go to attach the flow meter to an established tank, you will need to stop the pump for a time. When the water flow stops the microbiome will begin to die off. When, after the flow meter is installed, the water returns to circulating, the microbiome will bloom and consume a lot of the O2 in the water, which can cause the fish to produce a lot of ammonia. A, established, fluidized bed filter or an outside canister filter with an established, heavy, colony of microbes on the ceramic bits, can help with stoppage recovery. The fluidized bed filter being the best for recovery after flow stoppage. The fluidized bed filter should have been running for 6 or more months before stoppage for flow meter insertion.

Great info, thank you!

There were actually two tanks, both salt water. One had "pet" tropical fish, the other is a commercial lobster tank in a restaurant.

I know the tropical tanks are very delicate and must be perfectly balanced. Not so sure about lobsters...

Lots of simple flow sensors out there, normally connecting through 1/8" or 1/4" standard screw fittings. These sensors produce a pulse output which you can then read with the Arduino.

Algae can be a problem but a fish tank should normally not have algae in the first place.