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Discussion Starter · #1 ·
Hello All,
I've got a 90 gal tank that seemingly needs more and more frequent water changes as determined by the wifes complaint of the smell...

The tanks been up and running for 5-6 years and i've generally done a 25% water change every 2-3 weeks. Lately i've been having to change about every 6 days. I always use API tapwater conditioner and add aquarium salt. Other than that, no chems ever go into the tank.
here's some of the details

substrate is sand, no undergravel filter. It's probably worth noting that i don't vacuum the sand. I do occasionally reach in and stir it around by hand to smooth it out etc from the fishes excavation projects. Other than the sand, there's approx 75 lbs of tufa rock in the tank.

magnum 350 external canister which also powers biowheels
eheim classic 2215 external canister
aquaclear 110 power filter
filter media/pads are generally rinsed in tank water monthly
(also worth noting-the eheim and the ac110 were recently added. not as a response to any problems, i was just planning on removing the magnum canister and biowheels and have the eheim and the ac110 running for a few months to establish the good bacteria before i remove the others)

(6) tinfoil barbs, in the 6" range
frontosa, also approx 6"
(2) synodontis, again approx 6"
(2) other small africans, can't remember what type, they're 2" or less
giant danio

all the fish have been in the tank from the beginning. nothing new has been added. Lost a few giant danios over the years, maybe 4. Other than that, no issues, disease, illness etc.

I've never done a lot of monitoring of the water chemistry, but, i've got a few kits so i can provide some numbers
NO3 approx 80ppm and NO4 around 0.5ppm. these seem to both be high, just not 100% sure why or what to do about it.
chlorine 0
alkalinity (KH) approx 72
GH in the 300 range
pH 7.6-7.8
As i've not got much, if any, experience with the chemistry data, i'm assuming the above numbers are possible and correct.

If i'm missing any relevant info that would shed add'l light on the subject, please let me know

It seems possibly the problem with the water starting to smell is too much ammonia??
Is the problem as simple as an overstocked tank? Get rid of a few of the fish, keep up with water changes every few weeks and it's handled?

Any guidance you could provide would certainly be appreciated.

41,534 Posts
The nitrates are high, but...

Even tanks with very high nitrates do not smell. Look for another a dead fish or fragment of a dead fish.

Not familiar with NO4.

For the health of your fish change 50% today and 50% tomorrow. That will get you to a safe level of nitrates.

Then plan on changing 50% weekly or more.

210 Posts
You don't have that much of fish really, for a tank that size anyway. And your nitrates are not crazy either though they need a change. Sometimes canister filters can really stink things up and shoot out nitrates if they are not cleaned well. That is usually the culprit for me when it comes to smells especially if I leave town a long while then come back.

It's also possible it's just the new filters you added having some gunk in them and not yet having the bacteria built up to deal with that - that is, the tank may be cycled but that doesn't mean all your filters are, and those are always full of rotting gunk.

I would clean out all the filters decently. They say to wash them in tank water but I usually run them under hot water instead and don't seem to have any issues from that. Even if you boil your media there is going to be enough starter culture in the canister/hob to ensure it quickly recolonizes it.

Then I would vacuum the gravel well, and perhaps move around your decorations and clean and vacuum those areas, too. Or else save that for a next step for if the first ones don't work.

1,365 Posts
You didn't mention if you use any activated carbon in the filter. Activated carbon will remove color and odor from the water. I would pack some in the Eheim or in the carbon container core of the Magnum. Just be sure to change it regularly. It's only adsorbent for a couple of weeks to a month.

Rinsing the filter pads in tap water is perfectly fine. Filter pads are mechanical filtration and meant to be rinsed clean. Rinsing them in tank water is treating them like biological filtration. That was not the intention in the design of the filter.

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