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Thread: Substrate for an under gravel filter

  1. Substrate for an under gravel filter

    I am building an under gravel filter in a large tank and was thinking of using black landscaping lava rock for the gravel. it is much larger than what these filters are usually used with but with how porus it is I am thinking it will work well. Does anyone have any experience with under gravels and using larger rocks or can anyone think of an obvious problem with it?

  2. #2

    Re: Substrate for an under gravel filter

    the first things that come to mind are what kind of fish are you keeping and then the size of tank.

    under gravel filters can work well in the right application but you are seeing them used less and less

    give us an idea of the setup you wish to have and how you want to use it and what filters / pumps are going to be used ect..
    Found a big spoon to stir with...

  3. Re: Substrate for an under gravel filter

    It is a 125 gallon that will likely have 4 goldfish and I have 2 290 GPH pumps for the filter. I have researched under gravels and what is good or bad about them and I think they will be the best option for what I want, at this point it's really just a question of what substrate will or wont work well.

  4. #4

    Re: Substrate for an under gravel filter

    I would not use an under gravel filter with goldfish as they move the gravel around to much. That said most gravel that you can find at pet shops should be suitable.

  5. #5

    Re: Substrate for an under gravel filter

    I agree with TKD about not using an under gravel filter for goldfish. but if you do just the cheap gravel would be your best bet.. they usually have a couple buckets on used vic from time to time also..


    I remember seeing some black glass like stuff in bags from home depo a while ago.. just be caution about anything with super sharp edges as your goldfish will love sucking up and spitting out any gravel that fits in their mouth.. rounded edges would be idea.. if your thinking the very porous stuff thats in 1" size chunks for gravel you may find it becomes more of a bacteria colony than you might like..

    i guess what im trying to say is try it out but be cautious of these things and let us know how it works :)
    Found a big spoon to stir with...

  6. Re: Substrate for an under gravel filter

    I ended up using pea gravel-ish sized pebbles. if you've seen the quickcrete gravel in stores it's that stuff. And the filter is a really simple pvc pipe setup with a couple powerheads for suction (similar to this guy's setup - https://www.youtube.com/watch?v=eM51JzDnKQM )

    The pebbles are too big for the fish to really move around so I'm not worried about that. I plan to churn the gravel for water changes to avoid buildup of anything in there and I have some ideas for mechanical filtration if it becomes necessary. All in all it seems to be working very well and with the extremely low stocking I expect it to be very easy to take care of.

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