Running bio filter at different speed at night?

Discussion in 'Filters, Filtration and Pumps' started by Stickleback, 2 Mar 2010.

  1. Stickleback

    Stickleback Member

    I have a complicated filter setup because I have a low cabinet and so cannot buy a filter that is large enough, that will fit. I have made a filter from two unpowered pond cannister filters and a powerhead. The trouble is the aquarium is right next to my bed and the 3,000lph pump is too noisy at night. It's the so called Tunze Silence.

    Anyway I was thinking of running two pumps one 800 lph at night and the 3,000lph during the day. Would differing flow rates be a problem for the biofiltering?

    Many thanks

  2. AdAndrews

    AdAndrews Member

    Kidderminster, Worcs
    If you were using the filter to a descent capacity then doing that at night would reduce the ammount of bacteria in the filter, which could cause ammonia spikes-one thing you definatley dont want in a standard fish tank, let alone a fully planted one where it could cause algae issues.
  3. dw1305

    dw1305 Expert

    nr Bath
    Hi all,
    Yes the filtration would be the "wrong way round", this is partially because the CO2 production will be higher at night as the plants will be net producers of CO2, rather than consumers and the lower flow rate may lead to the water in the filter becoming de-oxygenated.

    A possibility would be to run an air pump at night, you need an air stone that produces very fine bubbles, ideally an “EPDM (ethylene propylene diene terpolymer) membrane diffuser type", and it would be best if the filter intake takes the bubbles into the filter, where they will have a long "residence time", allowing more oxygen to diffuse into the water (O2 is much less soluble than CO2)

    The only problem then would be to find a silent air pump.

    cheers Darrel

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