Help with cube tank, fish dying
Hello, I got my order of 3 fish yesterday, 2 clowns and a goby. Only the larger clown is alive as of this morning 08:50 and not looking good . Inverts and coral seem fine. Did the aclimation process and all fish seemed fine at first. After adding them to the tank they started to deteriorate. Added the fish to the tank at 14:00. The small clown died 21:00 and the goby 22:00. Both fish started darting around before death. I did two 10% water changes and created as much rippling on the surface as I could, also skimmer running.
Have not had any fish in for 2 months since the first tiny goby got stuck in the rocks and died (I think). Had the goby for a month with no issues and feeding nicely.
The fish store will be open in an hour. What should I get to try to save the clown? Better nitrite and ammonia test and charcoal for the sump?
90l cube tank
Rear sump with rough filter material, bioballs, skimmer.
35ppt salinity
nitrites and ammonia negative
8,2 ph
26,5 C
Lights have been off since adding the fish.
Thank you for any quick replies!