high nitrite levels

Question
I have been making 30% water changes, adding aquarium salt to the replaced water, and not feeding my fish(today was my sixth 30% water change and I have not fed my fish since Thursday), and yet the nitrite in my tank is still reading above 10.0. My Molly fish that I thought was stressed due to rapid gill opening/ closing, is still exhibiting the same behavior, but is fine other than that. We have an air pump going, as well. Do I continue not to feed my fish? Do you have any new advice? I understand that high nitrite levels are normal towards the end of my tank's cycle, but I just want to make sure I am doing all I can. I also was wondering on your comment about my betta fish not being a good community fish. Could you please elaborate?
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-----Question-----
I have had my 10 gal. tank set up approx. 6 weeks. My nitrite and pH levels have been high, and my nitrite level has spiked and been extremely high within the last few days. I have three mollies and one betta, and I am concerned that one of my mollies is in stress. Her gills are opening and closing constantly, while the other fish's gills seem normal. She is swimming fine, but hanging out alone when she normal is part of the pack. I have added salt, and done three 25% water changes in the last two days. I had added a pH decreaser to lower the pH level, and when it did not, I added a pH correct tablet, which also seemed to only temporarily lower the levels. I later read that this might be the problem. (I have changed the water twice since learning this info)please let me know how I can comfort the one molly.. it is my daughter's and she will be crushed if she dies.
-----Answer-----
Hi,
Your tank is probably still cycling, so high levels of nitrite are normal. This is very harmful to the fish though, so large water changes as often as possible is the best thing to do. I'd recommend doing 30 percent water changes every day or two until it is 0.0. Don't try lowering the pH, as Mollies prefer higher pH anyway. Bettas are not very good community fish, so I'd recommend taking him back to the shop if possible. Move the filter to the surface of the tank so the water is rippling quite a bit. That will increase the oxygen levels in the tank which will hopefully slow down his breathing.
I hope he survives.
Best wishes,
Kathryn

Answer
Hi,
Are you sure it is nitrite you are testing for, not nitrate? Because 10.0 nitrite is incredibly high, and would never get that high normally. 4.0 is usually the highest it gets to. Nitrate however, is safe under 20ppm. Does the test actually go to 0ppm?
Continue doing water changes, and if it does not go down any within a week buy a nitrite/ammonia reducer. Just squirt it into the tank and it should lower. I am not a fan of using chemicals but 10.0 is very high, so that should help.
The Molly is probably not getting enough oxygen. Mover the filter further up towards the top of the water so it makes more ripples in the surface. That will increase oxygen flow to the water.

Bettas are also commonly knows as Siamese Fighting Fish. It says it all in the name, anything that looks remotely like another male Betta will be killed. They are, by nature, very aggressive fish, even though they look beautiful. I must say though, some can be trained to be ok in a community tank, but you still have to be very careful.

Best wishes,
Kathryn