airstones, are they a Must ?

Question
chris... my question is about airstones in an aquarium.  i have a 30gal community tank. i have an undergravel filter with powerheads and a whisper hang-on filter.  i've had the tank for about 8 years and try to keep it as natural looking as i can.  

in the beginning i had an airstone that ran the entire lenght of the back of the tank, i did not like the looks of the wall of bubbles and eventually changed to an airstone in each back corner.  i now would like to get rid of the airstones all together.   

a local chain petstore said i didn't need the airstones as long as i had the powerheads pointing up towards the surface.  i usually dont' trust the chains but this guy seemed to know what he was talking about.  he said the air gets in the water by surface disruption, not the bubbles rising to the surface.  is this true ?  i would love to remove the airstones, but don't want to kill the fish.   just looking for a second opinion  : )    thanks for your input !

also, the tank is 30 gal long. it contains 1 pair breeding angels, 3 guppies, 2 balloon mollies, 6 cardinal tetras, raphael cat, and a farowella cat, do i have room for more fish ?  i'd like to add more cardinals or maybe rasorba tetras.

thanks again.


Answer
Hi Roger;

The fish store guy is quite right. As long as the power head or power filter water breaks the surface, you don't need airstones. Keep them on hand for emergencies though. Very important in a crisis if you have to remove the fish from the tank or they get ill and need more oxygen. I like them in my tanks because the water stays clearer and there is less muck hanging around. The filter picks up stuff easier if the water is more agitated.

The tank is really close to its safe population limit, but you could try a small school of rasbora hets or cardinal tetras. Maybe 5 of one or the other. Make regular water changes of 25% every two weeks or more to keep everyone happy and healthy. Vacuum the gravel at the same time. This is essential for healthy fish of any kind.

The absolute maximum population for any tank is two inches of adult fish per gallon, but only if you want to clean and change water every week. One inch per gallon is much safer. You can make changes every two weeks this way. Not overfeeding is very important too. Make sure the fish finish all the food from all areas of the tank in 5 minutes.

Followups welcome.

At Your Service;
Chris Robbins