My tanks smell...more than typical. I have an incredibly sensitive nose, which is a constant battle with the cat and dog poplulation of my house....but now the tanks are adding to the aroma. I expect some odor, but this is much more so. I think that I do normal maintainance of my filters....have mostly Penguins, one aquaclear. I squeeze the sponge in the latter in used tank water about every 3-4 weeks, replace the cartridges in the penguins every 4 weeks-ish. I tend to change one of the two one week, the other two weeks later to not mess with my cycle too much.
My water parameters are good, nitrite/ammonia 0, fight to keep my nitrates under 20, gravel vacuum with every water change...twice weekly.
I clean the impeller and stuff about every 6 weeks, and plan to do that today.
So, what am I missing....need to do?
Would adding carbon destink things...or is that a waste of time?

What's your water smell like? It should have kind of a "dirt" smell. Kinda earthy, kinda like after it rains outside. If it has a foul smell, then something's not right. Yeah, try some carbon, that may make it smell better, but if it's a foul smell,then you'll need to figure out why it's like that. I'm not really sure, but water quality when poor can make water smell weird.

yes. carbon in the filter is an excellent odor eater! in fact, because ive got quite a few tanks in my room, i use a small negative ion generator/carbon air filter to suck up all of the stray "fishy" smells of the tanks and extra equipment that ive got in here. it works like a charm! if youve got a very sensitive shnozz, you may want to look into these great little units. you can get them online pretty cheap too! just type in the keywords: negative ion carbon air filters. you should get some pretty good results with them!

hope this helps!

I like the answers above. Do you know your GPH in your tank? Movement of water might help. Carbon too.

Okay, thank you for the help so far...to answer questions, the smell is pretty much like an aquarium usually smells, just more so....aquarium smell squared.
Water parameters in all tanks are ammonia 0, nitrite 0, and nitrates 10-20.
Water circulation is 1). 20 gallon 1 330 penguin (3 baby orandas)
2). 40 gallon 1 330 penguin, 1 300 aquaclear (3 commons)
3). 60 gallon 2 330 penguins (5 commons--2 of them small).
I know that I don't have enough gallons for all those commons...but life is what it is...can't go bigger and they are better off then when I rescued them from my daughter's preschool...4 big ones in a 20.
Interestingly, the smelliest tank is the 20 with the most filtration and fewest fish.
I will get some carbon and see if that helps. I also will look into the air filter..thank you!!!

your filtration is excellent in ALL of your tanks. kudos to you!

just a little hint for the penguins:

you can re-use the filter pads for quite some time. because you have the extra media baskets and the bio-wheels, you dont have to worry about keeping bio-bugs alive on the floss. you can rinse the cartridges out under a high pressure stream of water coming from a tap. this should allow you to use the same cartridges over and over again for a couple months each (at least). well, the carbon looses efficacy rather quickly and it becomes somewhat useless. so, cut a slit along the top edge of the blue floss and dump out all the old carbon (you might have to worm your finger into it to get the carbon out of the bottom half). once that is done, you can add fresh activated carbon from the cartons that you can get from your local fish store. this will dramatically reduce what you normally pay for filter cartridges. those things arent cheap, you know?!

happy tinkering!

B) Yes, carbon is the answer. I have 2 Emperor 400's on my 58 gallon. I also bought 4 velcro closure media bags from www.drsfostersmith.com and I fill them with carbon. No smelly here!!!!

Thanx for all the help. And thank you for your kind words, Toothless. Hey, I read the info on this site and am a believer!!! Other than not providing 20 gallons per common....I follow the gospel!!! Okay, and I have 3 baby Orandas in my 20 gallon, rather than 2. That is actually Orandaman's "fault"...he sent me one more than I requested!!
Anyway..will be doing some surgery on my penguin cartridges tomorrow after a trip to Petsmart to buy carbon. Begone fishy odor. It can't be that bad, my husband thinks I'm nuts, he doesn't smell anything. Phewie!!!
Toodles!

NitrAte is the main culprit of the smell.. when you smell bad odour, that indicate high nitrAte content, and it is best if you remove them through partial water change too... Carbon may help to bring down the smell to only a certain degree and you will face the same problem once nitrAte accumulation is higher again.. and when nitrAte is so high, more problem will be introduced to your fishes too..

cheers

My betta tank smells earthy but not my goldie tanks. So thats the higher nitrate level in those tanks probable then? I have carbon in both their filters but still smells a little fishy.

i had an odor problem in my tank once.
the only thing different from my norm was the addition of StressZyme.
the odor was really bad, like nasty wet gym socks... that sat for a week... in a plasic bag... on a heater... lol not at all like an "earthy" smell

but frequent water changes over the next couple days and the tank didnt smell. i havent used the stressZyme since

Yah, ad some carbon to your filter, that'll do the trick!

so cycling tanks smell more than cycled tanks?