dying brittle star please help

[Alvaro_avalos]

i've had this little guy for about a month and hes in my 20 gallon tank recently it was looking like my hermit crab was chopping tentacles off which i found out hed a actual hermit crab so not even reef safe i isolated him but after turning on the lights today he looks to have lost more tentacles hes down to about half an inch on every side his disk is fully intact though i don't know if it was the hermit crab to start this or something else but before all this they got along i first noticed he lost his tentacles or the tips at first about 3 days ago then yesterday he lost the rest leaving about 1/2 inch i tested my water and my nitrates are 0 ppm my nitrites are 0 ppm and ammonia is 0 ppm my ph might be low my lfs said it was fine

 

[Sugar Magnolia]

How old is the tank?

 

[Alvaro_avalos]

its been up one year

 

[jayball]

its been up one year

Target feed every couple days for a couple weeks to see if he regenerates. Mine were loosing length on their legs and started recovering after a few target feedings. I guess I was not feeding messy enough for it to grab anything.

 

[Alvaro_avalos]

i target fed him since i had him i did it last night too i dont see any movement i have a suspicion all the chaos in my tank is from small worms not bristle:uzi: