new fowlr questions

hello everyone, im teddy and im new here on this forum and kind of new to saltwater aquariums,

ive had many many many freshwater tanks, and have two at the moment, ive had a agressive fowlr a few years back that was succesful but didnt have the time for it,

now i set my mind to a new 55g fowlr and have it all setup and running, its been running for alittle over 3 months now, but i have a few issues and questions,



my parameters are good but weird, 0 ammonia 0 nitrites 0 nitrates.. i say weird because ive had put in api stress zyme, no ammonia spike.. ive put in raw shrimp for a couple days, no ammonia spike.. i tried fishfood, no ammonia spike.. i mean ive waited enough for each to help the spike and added enough..

so i went ahead and added a couple green chromis and waited to see if that would make a difference but nothing happend, so i added 2 skunk clowns but all stayed in there for about a month but still no spike. so i thought maybe it was from the live rock i have about 40 pounds of live rock and 6-10 pounds of base rock.. as the days went on i took out the skunk clowns because theyre oh so aggressive , and added a pearlscale angel to the tank, a couple weeks later i added 2 saddle back clowns in there and they are just wonderful. they were all peachy till i added 2 skunk cleaner shrimps and 2 false perculas and a reef safe hawk to the tank.. the 2nd day i started seeing nips on the pearlscale's tail but thought maybe it was just the new clowns setting up territory ( and might i say , i know most of you are saying that i shouldnt add more then a pair of clowns in the same tank, but i swear to you there is no agression between the pairs at all ) the day after i saw the pearlscale with a huge bite on its side i could even see alittle bones, and soon after i took it out, the day after that i saw the hawkfish laying dead on the bottom of the tank with no nips or bites or anything. they day after that i saw one percula with a thin transparrent film just hanging on its side and died the next day, ive tested parrameters and and salinity levels, everything is the same nothing has changed, all is 0 and salinity is between 1.021 and 1.024



so now after seeing 2 fatalities and an injured angel im looking for help and answeres.



my questions are-

1- why are my parameters not changing or spiking?

2- what could of hurt the angel so bad, and what killed the hawkfish with no marks or being bullied, and the percula with the light film thing hanging off???

3- i feed my tanks a good qualtiy pellet and flake food, but i see the shrimps picking up and putting the pellets in their mouths but spitting them back out, is this normal or should i feed them somthing else??(the shrimps have been in the tank for 4 days now)

4- do you think a cleanup crew can be well in this tank?

5- can i add mixed shrimp specieces together with no problems?



please guys any help is welcome, thank you :)