stagnant / earth like water smell even after water changes ?

Im still getting a bit of a stagnant / earth like water smell even after doing water changes, just wondering if anyone else gets this and if this is normal, its a 4 foot fluval roma 240, im using the down pipes for filtration, but because these are both 1 side of the tank, I have a wave maker the other side of the tank to stir the water up to try and reduce any stagnant area's, im cleaning my sponges in my filters every month, im actually told this is too much and only needs to be done every 3 to 6 months, im doing 3 x 10% water changes a week, feeding every 2 days etc.

I am adding flourish and flourish excel into the tank for the plants, not sure if this is the cause.

I also had a bit of a brown algae bloom recently, but managed to get that under control by controlling the light a bit better and running my fluval 3w UV inline 24/7.

How's the actual tapwater smell, once the chlorine gasses off? I used to have tap with a kind of swampy taste - it passed all the tests and was fine for drinking, but you knew it hadn't come from a lab. In a tank, it could be a tiny bit gamey before a water change.

I agree with @GaryE, check your tap water. If that is not the source then open the bottle of Flourish and smell it. Does your water smell like the Flourish? How much are you using? If that is not the source then I would examine your substrate to see if you have any putrefying areas. I find it odd they filter uptake and return are next to each other. Is there some way to modify that?

Thanks guys, the tap water doesn't smell of anything, I'll check the flourish when I get home in a couple of hours, I'm actually under dosing with the flourish, it says to use 1 capful of the flourish excel daily per 200 litres, and I'm adding 1 capful daily to a 240 litre tank, the filter inlet and outlet being next to each other in the drilled posts is normal (image below), there's no way to modify it as I've not got anything to plug the holes up with.

An "earthy" (not overwhelming, though) smell after a WC is perfectly normal, I experience the same thing in all of my tanks.

On another note, how long has the tank been set up? Are you washing your filter sponges in old tank water (or treated tap water)?

How heavily is the tank stocked? You probably can do just 1 (larger) WC per week

Slaphppy7 said:

An "earthy" (not overwhelming, though) smell after a WC is perfectly normal, I experience the same thing in all of my tanks.

On another note, how long has the tank been set up? Are you washing your filter sponges in old tank water (or treated tap water)?

How heavily is the tank stocked? You probably can do just 1 (larger) WC per week

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Thanks for the confirmation, it's also quite a heavily planted tank, wasn't sure if that's what was causing the smell.

Overall the tank has been running about a year, with the same filters, but although I say a year, it was a 105 litre tank which I upgraded to a 240 a couple of months ago and just transferred everything from the old tank to the new tank, including my filter, then topped up with clean heated and treated water, and yes always rinse my filter sponges during a water change in the tank water that I've taken out.

I probably have about 40 fish in the tank, most of them are small, varying in the tetra range (neons, glowlights etc) , the biggest I have is 2 clown loaches which I wouldn't really call big either, probably 2 inches long at the most.

Yes, the smell is from the organics in the tank...again, perfectly fine (and normal) in a well-established aquarium

Do you have water change equipment, or do you perform WCs with buckets?

Slaphppy7 said:

Yes, the smell is from the organics in the tank...again, perfectly fine (and normal) in a well-established aquarium

Do you have water change equipment, or do you perform WCs with buckets?

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Great thank you.

Pretty much do water changes with buckets, or rather very large bottles, i have 2 X 25 litre bottles, one is heating up as we speak with clean tap water treated with seachem prime added to it ready for the next 10% water change later tonight, and the other 25 litre bottle is empty, ready for the waste water I take out, I'm planning on getting a bucket at the weekend to put the waste water into and use both of the 25 litre bottles for clean water so I can get water changes down to 20% twice a week instead of 10% 3 times a week.

A healthy tank should have that "biological" smell, sometimes quite strong if the substrate and decor have been disturbed recently. If it smells like rottenness (eggs, meat, fish, garbage) or if the smell changes drastically, that can indicate a problem.

If you have a nearby tap with a removable aerator, you could use a siphon hose system to perform WC's; makes the task MUCH simpler to accomplish, both in draining old water and refilling with fresh water

I use the Python brand, but there are others available

WhistlingBadger said:

A healthy tank should have that "biological" smell, sometimes quite strong if the substrate and decor have been disturbed recently. If it smells like rottenness (eggs, meat, fish, garbage) or if the smell changes drastically, that can indicate a problem.

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The only way I can describe it is it's a earthy like smell, like if you live near a big field and it's rained heavily you can smell the soil type smell in the air.

I have recently disturbed the substrate, as I had a brown algae problem that I was trying to fix, got it pretty much under control now, it was easy to see as my substrate is white sand, so gave it a good siphon and turn over.

Goose3080 said:

The only way I can describe it is it's a earthy like smell, like if you live near a big field and it's rained heavily you can smell the soil type smell in the air.

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That's exactly what it's supposed to smell like. It's the smell of biology happening.