Bad Smell??

[AmazonTankz]

My 15g tall tank has a bad smell to it, everytime I go to feed them and open the lid I can smell it. At first I thought I was some moldy food that had collected on the inside lip of the tank. I cleaned that up and do so often bad it still smells. It hasen't always been that way so could this mean something bad?? I have had so many problems with this tank before I would hate for something else to go wrong.
The temp is about 82F and the PH 7.8(Hard water) there is no ammonia or Nitrite in the tank either.

 

[dattack]

Do a big water change and or/run some carbon.

 

[AmazonTankz]

I recently did a 25% water change, b/c I thought the tank look really cloudy. Turns out it was just a white scum like alge on the sides. I've never had that sort alge on my tank before.

 

[Paul]

Change out your filter media. Try small 5 precent water changes every other day for about 2 weeks. And then go back to your normal weekly routine. Try cutting back on the amount you feed your fish. The smell could be from a build up of excess food on the bottom of the tank. Try vacuuming your gravel also. A tank should have a slight ordor, but nothing offensive.

 

[AmazonTankz]

Hey thanks a lot!