DIY Bio-Nitrate filter

Unfortunately the sand filter chamber was a bust when the flow reduced to almost nil. I suspect that the density of the packed sand after some time and biology reduced the flow.
I tried a quantity of sand about half as much and all was well, but flow nearly stopped two hours later.
I replaced the sand with polyester filter fiber. This should provide a good platform and water polish.

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Is the point of the second filter also to remove nitrates? If it is, I guess the very thing that allowed the sand to do its job was the very thing that made it impractical: the reduced flow rate. That's why the Seachem Matrix was a good choice, since it reduced the amount of oxygen that could reach the anaerobic bacteria, allowing a suitable environment in which they could perform their job, but at the same time, didn't obstruct, or at least not greatly, the flow rate. This, unproven as of yet, but still in theory, made the Seachem Matrix the best choice for a nitrate filter media. So, in light of that, why did you build a filter without the Matrix? Why one with sand, or polyester fiber?
I guess I don't understand what exactly you were trying to do, but it could also be that it's 1:00 in the morning...:coffee:
 
Is the point of the second filter also to remove nitrates? If it is, I guess the very thing that allowed the sand to do its job was the very thing that made it impractical: the reduced flow rate. That's why the Seachem Matrix was a good choice, since it reduced the amount of oxygen that could reach the anaerobic bacteria, allowing a suitable environment in which they could perform their job, but at the same time, didn't obstruct, or at least not greatly, the flow rate. This, unproven as of yet, but still in theory, made the Seachem Matrix the best choice for a nitrate filter media. So, in light of that, why did you build a filter without the Matrix? Why one with sand, or polyester fiber?
I guess I don't understand what exactly you were trying to do, but it could also be that it's 1:00 in the morning...:coffee:

The first canister (see pic) is a mixture of Seachem Matrix and Seachem De*Nitrate (2 liters De*Nitrate, 1.5 liters Matrix) - both should work great with a flow rate of 3.5 gph that the Tom aqua lifter pump provides. The second canister was/is just for extra filtration and possible additional nitrate removal and/or dissolved solids trapping. Water siphons from the tank into the first canister, flows through the media, then into the second canister, through the media and then back to the tank.

The thinking here is to better filter/purify the water to reduce the frequency/volume of water changes because I can no longer use unfiltered/untreated water for water changes (which is why I will periodically also use carbon. purigen, etc in my AC70 filter as well).

The biggest reason for weekly (sometimes large) water changes is to remove/dilute nitrates. If we can [better] manage tank nitrates while also better filtering/purifying the water, we can reduce volume/frequency of water changes and still have excellent water quality.

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Oh, I thought you changed the media in both filters to sand. Ok, so the second filter is acting as a normal filter would, while the first still has the Seachem Matrix. Got it.

In that case, why don't you swap it around, so that the water goes through the polyester filter before the Seachem? That way any gunk that the filter pulled in would be filtered out by the polyester before it got stuck in the Matrix, and you would be able to clean it out without disturbing your colony of anaerobic bacteria.
 
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The siphon tube is in the top inch or two of the tank so there shouldn't be any detritus getting to the bio-filter to worry about. The secondary canister was more of an extra added level of filtration to deal with dissolved organics and such (you want/need organics to feed the bacteria). I decided to go ahead and get sponge material, so I removed most of the fber fill in favor of sponge. The sponge material should be an excellent platform and still provide good flow. The sponges I used were AC70 sponges that with a little convincing fit really well...
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