question

[kwok]

My tank is doing some funny things and i would like some help.

it's a 20 gallon FOWLR and i currently have two small clarkii clowns and a scooter blenny and 6 hermit crabs and 1 snail.

my fish are not moving much and they seem to be breathing heavily. they don't go after the food during feeding time.

my parameters are:

salinity: 1.023
temp: 25 c
ammonia: 0
nitrite: 0
nitrate: 0
ph: 7.8-8.0 - i know it's a bit low but it was 8.3 just a few days ago.

i also had a sex line wrasse in it a few days ago and it died last night. all i did the last 2 days was a 20% water change and i added a new powerhead. i use water conditioner for my water changes. i'm not sure what else to test for my tank. any suggestions?