Questions about water quality and filtration

　　The top filter fish tank of 80X40X54 has only been raised for two days. Because the top filter is too small, only 4 layers of white cotton can be placed. The filter is really weak!The water quality has always been above the standard of ammonia nitrogen and nitrite. Later, the self-adhesive tank was changed to the upper filter. After the modification, the water quality of ammonia nitrogen and nitrite were basically zero.Mix, then measure the ammonia nitrogen and nitrite are above the standard, and then change the water and add digestive bacteria, until now the ammonia nitrogen has not dropped, about 0.4mg/l, the filter material has not been moved, at least only the white cotton has been washed, and the white cotton pad is raised away from the water surface, the living cotton bacteria house has not moved, please help, see what is going on, what should I doRow?
======== Xianglong Aquatic Alliance Fish Friends Comment =====
Earl of the Dark Night Comment: Increase the flow of the pump, the filter cotton is to be washed, and the biochemical cotton cannot be washed casually!It is best to add some bacterial houses to the biochemical cotton Nagar! You have too much biochemical cotton
shibin18 Comment: Feed less, change water frequently
a277469421 Comment: Feed less, change water frequently, and the digestive system builds well in about a month.
Originally like tossing Comments: This looks not very beautiful
Hualong Engineering Comments: Lou Zhengjie, agree
L-H-R Comment: Change water frequently, explode oxygen, and feed less
anson2014 Comment: Your arsenal is ok.Raising the silver dragon is too small.Filter to add a dry and wet separation box, increase the power of the pump, change the water several times
ganqingyuan Comment: It is too small, no fish have been raised, so buy a small tank to practice
ganqingyuan Comment: I have opened the tank for three or four months. The water quality was normal some time ago, and it started to deteriorate last week.
49055419 Comment: It would be better to add a filter bucketCan Red Dragon Fish feed Qianhu feed?,Which brand of domestic koi feed is good%What kind of goldfish feed is best%The most expensive dragon phoenix koi fish price?How much is a pound of chicken feed/Unified Koi Feed Price List&Can the arhat fish only be fed by Qianhu?)Goldfish feed red insects or feed$How about unified koi feed(Homemade Arowana Fish Food Fish，Questions about water quality and filtration。