I am setting up a small 4g aquarium. I have a large filter from my old tank that I want to reuse. Is there a disadvantage at putting 50g filter into a small tank?


2 Answers 2


If you put shrimp in the tank make sure that you have a protection against them being sucked into the filter.

If the filter is made for a 10 times larger aquarium it will consume a multiple of the necessary energy for the small tank. Check the power consuption. There're reliable filters for 20 l tanks with 2 W consumption. The investment of buying an (eventually second-hand) matching filter can compensate within one year already.

And like @Diether pointed out: the pump might be so strong that the whole aquarium will be a water strom.

  • 1
    On top of that, I would imagine that you'll get a small storms in the small tank. There should be some water circulation, but with such a big filter, I assume it will be a little too much. But you can try it out.
    – Diether
    Mar 13, 2017 at 9:06
  • I am planning to add shrimp to the tank. So, if I get a smaller filter to match the tank, and put up protection (a sponge cut out to fit the "vacuum"), would that significally lower the flow? I don't have to compensate for it with a stronger filter?
    – tuco
    Mar 13, 2017 at 15:12
  • If you get a new filter, just get a "shrimp-safe" one and you don't need to worry about that. I recommend the Dennerle Nano series with 2 W. Generally the filter pumps are quite strong and you won't manage to significantly lower the flow no matter what you put in front of the inlet. It's a hundred times than more important than the filter dimension that you observe the functioning of your filter by checking water values and cycle your aquarium before putting living beings inside. Mar 13, 2017 at 19:30

Putting a 50g filter in a 4g aquarium is not good. There is a reason filters are rated by the gallon. It will be way to powerful for any fish you put in there. Small fish will be blown around, as if in a tornado. If you insist on using it, stuff the filter area with the extra filter pads you can get at fish stores to slow the flow way down.

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