Ammonia levels still? About to give up :-/

Ok so its me again with the ammonia issue. I honestly am about to just stop worrying about it. In going on nearly 2 weeks, I have done THREE 50% water changes, with 20% changes in between. Everything is alive and fine, but the ammonia will not go below .25 for anything. Strangely, in the hour or 2 after a WC, ammonia actually has been going up to .50, but then is back down to .25 by the next day?? What in the world is going on? I am very careful, I use rodi water, and I very gently vacuum the sand so as not to disturb it too much, I only feed 2 VERY small pinches of brine shrimp a day, and most of it is eaten before it settles. What else could it be if it is not a problem with my test kit? Nitrites at zero, nitrate is between 0 and 10 on the test. Everything is fine except that my emerald crab ate my peppermint shrimp. Anemone is wide open and looks good. It even takes krill pieces from my hands. Snails are still active, corals are open and haven't moved, flame angel is tearing off algae from the rocks, 2 clowns are active. WHAT is the deal??



Oh is anyone needs the info again:

75 gallon, set up 4 months ago, 2 months to cycle

1 flame angel

2 occ. clowns

1 firefish

1 cardinal

1 lawnmower blenny

3 coral frags (red mushroom, zoanthid, green star)

anemone

1 zebra turbo snail

about 7 various snails, margarita, cerith, etc