Knowing When A Filter Is Undersized Question

Discussion in 'Filters and Filtration' started by ManSkirtBrew, Apr 17, 2019.

  1. ManSkirtBrewNew MemberMember

    I'm running my 46 gallon tank with an Eheim 250. I got it through my LFS before I knew much about filtration or tank turnover rates.

    The 250 is rated at 440lph (116gph), which is clearly less than the 5-times-per-hour recommended turnover rate.

    However, my water is crystal clear, my chemistry is stable. My LFS feels like the fact that the plant is well planted and has a smallish bioload (12 tetras, 4 mollies, 10 shrimp, lots of snails) that things should be just fine.

    I'm inclined to agree, but I'm curious what the signs of needing more filtration would be. I've only had the tank for a month, so I know a lot can change and I want to be ahead of the curve. I assume nitrates would start creeping up first, but anything else I should be on the lookout for?
  2. RtessyFishlore VIPMember

    Signs of low flow in the aquarium, like if a corner or two is stagnant and has protein film.
    High nitrates are not a sign of inadequate filtration, and filters don't remove nitrates. Ammonia or nitrite would be signs of inadequate filtration as the filter would not be powerful enough to quickly turn them into nitrate.
    Excessive waste buildup on the bottom is also a sign.
    Oh also, planted tanks should have 8-10x the flow rate of the tank, so more not less ;)
    IMO, you're probably fine, if it ain't broke, don't fix it.

  3. ManSkirtBrewNew MemberMember

    Oh yeah good point about the nitrates. If they were creeping up it would be a sign that the filter is doing its job converting ammonta->nitrite->nitrate.

    I did add a small powerhead to move water around, which may be why I haven't seen stagnant water yet. Time will tell!
  4. IslandvicWell Known MemberMember

    If you look at videos of tanks and fish rooms from breeders, almost all of their tanks run only sponge filters, with the occasional Aquaclear or Penguin 350 as supplemental filtration.

    Professional (and amateur) breeders would not rely on sponge filters if they didn't work.

    Take a look at Prime Time Aquatics and Aquarium Co-OP videos on YouTube of their fishroom tours. Almost all of the tanks run sponge filters, with no magic turn-over rate.

    If your water parameters are good then the filter is supporting the appropriate size of colonized beneficial bacteria.

    More flow may help with pushing detritus and muck off the substrate so it can be sucked into the canister. That is more for aesthetics because a quick surface vac with a gravel siphon during water changes can cure that.
  5. ManSkirtBrewNew MemberMember

    Thanks Islandvic. That makes a lot of sense. So then using the example above of 8-10x turnover rate for a planted aquarium, is that just to ensure that there is good flow for the plants, and not for good filtration?
  6. RtessyFishlore VIPMember

    Yes, mainly because the plants can block the flow, so it's a good idea to add a little extra, so your powerhead should be perfect!
  7. IslandvicWell Known MemberMember

    @ManSkirtBrew , I couldn't say.

    Some other the turnover rate suggestions may come from the fact that a filters flow rate in gph stated by the manufacturer is only rated at the pump or impeller assembly.

    The specified rate usually does not include any media in the filter, or the head pressure or friction loss in the tubing for canisters.

    A filter rated at 300gph mainly flow 50%-75% of that once you insert the media.

    It may be even less if you add extra DIY media to the filter.

    So the turnover rates may be high to factor in for that, but I am only speculating.

    I would rather have water flow at 75gph through this......

    Versus water flowing 150gph through this......

    So in my opinion, turn over rates are subjective.
  8. IslandvicWell Known MemberMember

    @ManSkirtBrew , i had a couple of questions about your Eheim 250....

    Is it the newer grey colored +4 model, or the classic green style 2215 model?

    I ask because I found a 2215 Classic model on sale and was tempted it buy it. I believe the 2215 Classic was also called a 250 Classic.

    I agree with @Rtessy about the powerhead.

    A YouTube channel I follow that deals with our hobby and cichlids, Ben Ochart, has a power head on a timer mounted I believe on the side wall lower toward the substrate.

    The timer turns it on a few hours and back off a couple of times during the day then off at night to give the fish a break when they rest.

    Ben advised he set it up like that so the power head can help blow the detritus and muck up off the substrate so the intake of the canister and overflow for sump could suck it all in.

    He claims it works well.

    I think he had a decently powerful powerhead since it was an African cichlid tank, and they like water flow and produce a lot of waste.

    Your smaller powerhead will work just fine since your tank is smaller and not stocked with a huge bio-load like his.

    You may have to experiment with adjusting the positioning of the power head, so it can stir up anything that settled on the substrate.

    Good luck, let us know how it turns out!
  9. ManSkirtBrewNew MemberMember

    It's the classic green 2213 model.