larger foam, foam filters???

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Magnum Man

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Jun 21, 2023
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Southern MN
so going into my 65 gallon Tilapia breeding / fry tank I plan to put 4 larger sponge filters, one in each corner ( there could be 3 or 4 females worth of fry to raise up before they go outside, so I'm going for overkill on the biological filtration...

these are the filters I'm looking at right now ( rated at 60 gallons each, but seems too small, so I'd use 4 )

in the reviews, there is a complaint that most foam filters use a finer foam, & clog up to often, and coarser foam is both better at function, & requires less maintenance... I copied the comment in the review, & guy seems logical, hence my desire for discussion

"The foam used for the filters is way too high in density it is well over 30 PPI (PPI= pores per inch).
I must clean them at least every 2nd to 3rd day because of the ppi count. they are more for polishing water not to act as a full-time filter.
I would not suggest this type of filter to anyone unless they want to use it for water polishing.
a lot of the foam filters sold on Amazon are the same, I don't understand why they sell such high-density high PPI-rated foams as a long-term filter. I can not find a decent foam filter with foam density like that of an aquaclear foam rated at 20 PPI except the hygger one with the clay and foam media. I should have got those instead, these filters are only good for polishing water not as a typical filter that is ideal for aquariums. the ideal PPI on foam for aquariums is between 10 to 30 PPI 10 being course 20 medium and 30 fine anything else higher is more for polishing water and short-term use."

so I'd like to talk about that... I did find some filters with coarser foam, but those look like mad science lab equipment... the filter linked above looks fully disassemble able, & though I haven't found a coarser sponge to fit this particular filter, I think I can wrap a sheet of coarser foam, cut into strips, around in place of the factory finer sponge, if that was in fact deemed better, I previously bought an assortment of black silicone rubber bands that I have found multiple uses for in aquariums... thinking one or two around the rolled up sheet of coarser foam, would be more than functional...

I did find this sheet foam, which could be cut in strips, & wrapped around the base, in place of the factory foam... I'm thinking a couple wraps, but that would depend on the thickness of the foam sheet I end up with...

thoughts on coarser or finer sponges for sponge filters used in aquariums??? in this case housing adults during spawning, then raising fry into fingerlings...

of course there is a huge difference in solids & bioload between spawning fish, & fry in the tank by themselves... so if it makes sense, the coarser sponge might be better with the adults in the tank, & the finer sponge might be better with only the fry in the tank... just wondering about thoughts an the ability of each to hold beneficial bacteria, and maintain acceptable water flow through the sponge
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This seller offers sheets of several sizes & several degrees of coarseness and lists them by PPI

Bigger holes in sponges doesn't necessarily mean better filtration. Quite often you get a lot of gunk drop out of the sponge when you lift it out of the water. Sponges with smaller pores don't drop as much gunk when removed from water.

Smaller pores/ holes in the sponge give more surface area for the bacteria to live on.
I like a stiffer sponge with medium sized holes, like the Swiss Tropicals poret stuff.

Tilapia have been known to eat sponge filters.
@Colin_T … I guess IMO, sponges should be used for beneficial bacteria media, and if I’m looking to remove wastes mechanical filtration does a better job of that, and I would want to add a mechanical filter, once fry are big enough to not get sucked into it… I have a bunch of those foam tips/ covers for my mechanical filters ( I was missing a screened tip to fit one of my big H.O.T. canister filters, and thought the foam would be a great replacement, I bought a couple packs of medium porosity, but pulling a high volume of waste through them, plugs them up weekly or sooner) the whole point of the beneficial bacteria, is it has to be exposed to water with ammonia and or nitrates to consume correct??? If the foam on a foam filter doesn’t allow water, or enough water to flow through it, the bacteria will only live on the surface, or areas within the sponge that allow sufficient water flow… if the foam is too coarse, water flows through, but there is limited surface area within the foam for it to attach… ideally if the foam was as tight as the “right” amount of water would pass thru, and no solids blocked the flow, it would be the most effective…

I’m just wondering if enough water passes through the foam on some of the tighter foams, or if it ends up just pulling it through the thinner areas and around the edges, and the centers of the foam blocks end up devoid of Beneficial bacteria, even before they start plugging with solids???
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