ammonia wont go away

Question
Hello Jaymie,

I have an established 20 g freshwater aquarium thats been running since the beginning of April. I do have more fish then what some may suggest but I do water changes once a week. I have 3 gouramis, 6 corys, 2 cherry barbs, 2 tetras, and a killifish. I've tested the water on a regular basis and for the past 3 weeks the ammonia level has not decreased but the nitrate/nitrate levels are basically zero. Now I got my water tested at my local petsmart and petco locations. One said my water was so toxic it was off the chart and another said just the ammonia was high. I've been doing almost %500 water changes every 2 days for 2 weeks and my ammonia reading is till high. The fish are acting normally, still have their bright colors, getting fed a small amount each day, but  i noticed they are pooping like crazy which from what I understand is from high ammonia levels. I use Seachem Prime to treat my water. I do not know what else to do, the ammonia level doesnt seem to want to lower. A very frustrating time for this fish owner. If you have any idea what could be done, any tips or suggestions would be greatly appreciated.
         -James

Answer
James,
If the water changes are not bringing the levels down, there might be a problem with the filter. Also, the water changes should be done daily when ammonia and/or nitrites are up. API has a product that helps with ammonia. I normally would not suggest using it, but in this case it might help. I would check the filter and see if maybe it's not working. You are over stocked and that makes the filter have to work harder. I would also suggest a filter made for a larger tank. With the over crowding, do your water changes more often than once a week. If a new filter does not help, let me know. When you do change the filter. let the media float around in the tank for a week so that the beneficial bacteria sets in so that the tank does not go through the cycle process again.