Fish keep dying, except starry blenny

[doctordox]

I hope that I am in the right part of the forum for this. Apologies if not! So long story short, in December I had a 3 month old tank, with a handful of clown fish and I added a starry blenny. All was totally fine, and suddenly in January, after I was aggressively cleaning the tank (I initially thought I moved things around too much), and I came in to my office where my tank is at and all of my clowns were dead, but the blenny is fine. So fast forward months later, Ive lost a bunch of Chromies and a Wrasse. My inverts, and Blenny have zero issues.

Every fish I add, dies within 48 hours.

Water tests totally fine really, but I had an algae breakout that was bad (now eliminated basically) and I think I had like zero nitrates in my tank because of that.

Could these fish keep dying because of a lack of nitrates in the water? IM so confused, and im starting to get upset over this. I love my tank. The Blenny is in heaven with the remaining algae, and he seems to be totally fine after all these months.

Ive changed my charcoal out multiple times, ive done big water changes. Any suggestions? Im very very confused as to what to do. Even local fish stores are a bit confused by why my water tests basically fine, but yet nothing survives.

Ive thought about just doing a huge water change, usually I do 10 % change. Its a 55 gallon tank, no sump just double filters and I dont do corals (yet).

I appreciate all and any responses!

 

[jaganshi066]

Sounds like we have a newbie here, he/she is unaware that blennys are killing machines. They can and will kill any fish In there territory

I don’t know about the newbie part but blennies are crazy territorial, in my opinion worse than dwarf angels