Oxygen level and Filters

Question
Hey Nori,
I have a 10 gal. tank. It wasn't till I set it up that I found out it would have been easier to start with at least a 20. I plan on upgrading but for now I have 3 community fish and an algae eater. I am concerned about the oxygen level. The Danios swim right at the surface and the black fin shark spends much time there as well, also he spends alot of time hanging around the filter. The filter came with the package. It is called Whisper and is for 5-15 gallons. Is this powerful enough. Without those bubble stones are they getting enough oxygen and is the filter the only source that is putting oxygen in the water. It doesn't seem to be making many and I changed the filter 3 weeks ago. Just learning so thank you for your patience and your help.

Cheryl

Answer
Hi Cheryl,
Thank you for your letter and welcome to the wonderful world of tropical fish care. (Please take that with a ;-)
You will need to upgrade someday because plecostimos can grow up to 13 inches long. Anyway, worry about that later. The main thing is the state of the little critters right now.
You could get bubbles, and I believe you should, but the root of your problem is probably over feeding. Cut back to one flake per fish per day. Give the plecto a spirulina tablet once a week. Remove any uneaten spirulina tablet after an hour. As the fish grow you can increase their food to about one flake or pellet per day per square inch of fish.
Also, use Cycle in the tank. It is not a chemical, but organic biology; friendly bacteria to make it more like a natural environment.
Do not use aquarium supply shop medicines and chemical treatments. They cost a lot and usually don't help.
Reducing the food is most often at the root of the problem and adding chemicals to that muck does not help.
So, if things are really bad, follow the emergency care instructions at the bottom of the page:
http://steamboats.com/aquarium.html
Please print the page out for future reference.
If you want to discuss further, please write back.
Nori