using canister filter as a denitrator - success

Here is an account of my attempt to reduce water change by denitrating the water.

I used 2x Eheim 2028 connected in series. The first canister carries the normal filtration material and outputs into the 2nd canister. The 2nd canister baskets are arranged from bottom up: Eheim ceramic rings, Eheim substrate, Eheim substrate. No filter wool used in any cansister. The difference in the 2nd canister is I turned around the bottom 2 baskets so that water flows normally through the first basket and exits from the first basket. This creates a semi-stagnant reservoir in the bottom baskets, much like a DSB in salt water sumps.

The first canister robs the water of O2 by aerobic bacteria. When the water enters the 2nd canister, the water is much O2 depleted. By having a semi-stagnant reservoir in the bottom 2 baskets, anerobic bacteria thrive and reduces NO3 to N2. The bottom 2 baskets must be loosely packed so that water diffusion takes place (in DSB, the critters perform the diffusion by burrowing). The Eheim substrate provides an incredibly large surface area for bacteria colonisation.

In a classical freshwater denitrator, you'd have to reduce the flow rate to a mere trickle.But in my case, I think it's not necessary as no matter how high the flow rate is, the 2nd canister's bottom 2 baskets are always in semi-stagnant water. The idea is more to deplete the water of O2 in the first canister by reducing the flowrate.

I seeded the filter substrates with Ocean Free Bacteria. It's 2 months since I changed the water in my 6x2x2 tank housing 1 aro. During that time, I top off evaporated water only. pH 5.9-6.0, kH 2, NO3 12ppm. The aro is feeding normally on MP. I also occassionally add S7. No other additives. 2 power heads in the tank to circulate the water. No additional aeration.

Bro, I must say that is a very ingenious way to create a DIY denitrator. What was e nitrate level b4 u used this setup ?

Before I tried this method, the NO3 was above 100ppm, the test kit turned red immediately after the reagent was added, instead of 20 minutes later.

Now the test kit remained light yellow (like urine).

Seem like u had it made. Just that the cost would be quite high if to use two 2028 canisters. Maybe a bit of diy with PVC piping/fittings may help to save a canister & operation cost.
On water changing, I think it should still necessary to be made regularly, though less frequient. There are probably other waste that need to be diluted in the tank too.

Originally posted by sorcerer
Before I tried this method, the NO3 was above 100ppm, the test kit turned red immediately after the reagent was added, instead of 20 minutes later.

Now the test kit remained light yellow (like urine).

I'm going to try your method since I already have 2 canisters, but with a twist. Instead of turning the baskets around, I'll remove all the baskets instead (I'll pack the substrats in nettings.) It should work too. The netted medias will be placed on the canister's floor upwards.

I got a question. Since I will be using existing ehfisubstrat already inside the canister... should I kill the aerobic bacteria first, or let them stay?

Originally posted by happybuddha
I'm going to try your method since I already have 2 canisters, but with a twist. Instead of turning the baskets around, I'll remove all the baskets instead (I'll pack the substrats in nettings.) It should work too. The netted medias will be placed on the canister's floor upwards.

I got a question. Since I will be using existing ehfisubstrat already inside the canister... should I kill the aerobic bacteria first, or let them stay?

The aerobic bb will be dead once they r in anaerobic environment.

i hv ever tot of connecting 2 canisters also, but hv not tried... need $$$ for another set.

do u hv to run both together? or just one is enough? if only oneis running, which is the one u run?

wish to hv a better understanding, can u post a picture to show how u "turned around the bottom 2 baskets".

many thanks.

Just want to amend my previous post.

I think "no basket" may not be a good idea. Tiny lose substrat could be sucked up and damage the impeller! I'll leave the trays in, with a layer of fine wool on the top-most basket to trap large debris.

In any case, I'll get more substrat to place them under the lowest basket.

[BarraCuda™]

IMO, its not cost effective. Its much cheaper and easier to change the water

Originally posted by SIAC
i hv ever tot of connecting 2 canisters also, but hv not tried... need $$$ for another set.

do u hv to run both together? or just one is enough? if only oneis running, which is the one u run?

wish to hv a better understanding, can u post a picture to show how u "turned around the bottom 2 baskets".

many thanks.

U need to turn both canister on otherwise e water frm e 2nd canister will not flow bck to e tank. I'm also quite confused abt e baskets arrangement of e 2nd canister may be becos I've not used Eheim 2028 b4. But my previous experience with other model of canister, it was not possible to turn e baskets around cos if u do that, u won't be able to close e canister.