Beautiful, but Smelly, Tanks

Question
I have a 55 gallon tank and a 29 gallon tank.  The larger has 4 goldfish, all in 4-5 inch range, a Red Oscar about 5 inches, an African Black Clawed Frog, an Apple Snail, one Pleco and 3 black catfish with sail fins.  The smaller is filled with guppies... too many to count (most of them are under 1/2 inch long), 3 Cory Cats and one small Pleco.  Both tanks are beautifully crystal clear.  Both tanks have been up and running since 3/19/06.  Both tanks were up and running previously in our first home.  We moved and since then the smell coming from the tanks is so bad!  How can a tank so beautifully clean looking smell so bad!?  I love these tanks and all the fish, but, I am at a point that I cannot stand coming home to that "pond" smell and I'm thinking about getting rid of them.  PLEASE HELP!!!

Answer
Dear Camille,
No healthy established aquarium should smell enough to drive you out of the house! This is a very clear and scary indicater that the water quality is not good at all.

What I must first clear is have both your aquariums been cycled? That means, before adding all the fish stock at once, you added only 1-2 fish and allowed plenty of time for special beneficial bacteria who convert harmful fish waste to less toxic substances--establish. I don't mean to drill you on this. But it is very important to know. You may have had your aquariums cycled before but when moved to the home, the bacterial colonies could have been wiped out if the tank, gravel, filter, and decor were allowed to dry out or were cleaned. This of course causes toxic ammonia (the by-product of fish waste) to build up and without beneficial bacterial colonies, it will be intolerable to all but the hardiest fish, and even they will perish. Leading to the fact that you have very hardy fish. They may be suffering also. Not even the hardiest can stand ammonia long term. This is why the first thing you should try to do is test your water for ammonia when something seems wrong with your beloved fish or the water looks or smells odd. Testing for ammonia is easy and simple. Hopefully if you have test kits for ammonia (found at local petstores) this will determin if you have an ammonia spike from an un-established biological filter (the bacteria).

~*~The first thing you should do ABOVE ALL. Is a 50% water change. Especially for the Oscar aquarium, I know oscars, and have had experience with them for many years now. And everybody knows what big polluters they are. They can pollute an aquarium within a day in a small or overcrowded tank. They are lovely, personal cichlids, but failing to due those vital twice weekly water changes guarantee to bring about illnesses like the dreaded Hole-in-the-head or commonly called "HITH" for short.
All fish appreciate water changes and because your 55gallon is well stocked (unfortunately too well-stocked) you need to do twice a week 50% or larger water changes to insure your nitrate levels (the end product of the bacterials work) are in check which insures healthy fish.
Unfortunately your current 55 gallon aquarium setup will not last long with the amount of fish whom all put a big bioload on the system. The four goldfish themselves, need a 55 gallon just for them (they can grow much larger) and put out big bioloads. Oscars may be the worst, ONE oscar is more than enough for a 55 gallon just by himself. I'm not for certain what species of catfish you have put they could be Pangasius or silver tipped shark catfish..Both these beauties grow large and need space. The two both need salty (Brackish) water to really thrive.
Please know I am not trying to tell you, you are doing it all wrong. Or trying to drill you. But I am speaking from my experience in the past and present.

Just please realize, with the fishes best interest in mind, that you will certainly need to be doing some thinning out of your population soon. It may be working out now just fine but as the fish grow to maturity and your Oscar wants his own space and territory (and he will be 12 inches when grown) it may be a total disaster.

But lets get back to the real business for now. If your aquariums don't have ammonia, the large amount of other pollutants are certainly causing the aquarium to smell. Healthy aquariums have little or no smell until you really lean in and get a good whiff, and that smell consists exactly like freshly dug earth. It's a very nice smell but is only limited to the very surface of the water and the filter...Never in the vicenity--even worse, running you out of the house.

So please, please, please change 50-75% of both aquarium's water. Use a large aquarium siphon and hose to siphon the water out. *You must insure that the replacement water you are putting in is equal in temperature to that of your aquarium and is properly dechlorinated with a water conditioner. Use an aquarium thermometer to accurately measure the temperature of the replacement water and adjust the facets to match the aquariums. A few degrees warmer is fine and generally not harmful. But never add cold water. Flucuating temperatures stress all fish.
You may have to do another water change the next day or so to dilute the pollution that is in your aquariums.
This should help your smelly water problem.

And you shouldn't have smelly water all the time. With the high population of fish you will have to continue with twice weekly water changes of at least 50% or more, testing your water is a good indicator of how much you actually need to change. More is always better, as long as the relacement water is always insured to match or be almost evenly close to the aquarium's temp and be dechlorinated always. Nitrates are one good indicator. They should be 20ppm and preferably less. And absolutely no ammonia or nitrites ever. Healthy, established aquariums have no traceable amount of ammonia or nitrite.

If your aquariums are still cycling (which ammonia or nitrite readings would indicate) this is a big serious problem that needs many water changes and extremely careful feedings until things are in order again.

For now, I hope you can test your water...And you will certainly need to do a very large water change.

Clear water doesn't ever guarantee good water. Testing your water is your best bet.

Let me know, if you don't mind, how things improve after a few good size water changes and if you can test your water for ammonia, nitrites and nitrates, if you would kindly report the readings back to me that would be greatly appreciated.

If you have anymore questions or concerns, feel free to email me. i will be more than happy to help.

Best wishes and happy fishkeeping!
Karen~
note:
(If you haven't done water changes in many weeks, a massive water change can stress out fish dangerously. But if large water changes are done frequently and they are ten times better than smaller changes, they are not dangerous. With an aquarium that hasn't had a water change in many weeks, smaller very frequent changes are in order to avoid shocking the fish with totally new water.) ;-)