Can't keep certain fish alive.

[gsw0716]

Just wanted some opinions from you experts. I have a 30 gallon cube. It's been running for around 14 months. I've had the same livestock for a decent amount of time, but when I try to add one more additional fish, that fish dies within a month. I didn't see any bullying, my existing fish are pretty chill. Here's some info of what's in my tank and how long they've been in my tank.

Pair of Ocellaris Clowns. Have had for over a year
Watchman goby with pistol shrimp. 9 months or so.
Tailspot blenny. Had for a to 7 months
Chalk basslet. Owned for 5 months or so.
Pair of cleaner shrimp. Owned about a year
Gold banded shrimp. Owned around a year.

Over the course of the past 3 to 4 months or so, I've tried to add one more fish, (not at once) but with no luck.

Firefish goby, disappeared after a few weeks
Hectors goby. Died within a week
Clown goby disappeared after a month or so.
Court Jester goby. Disappeared after a month or so.


Maybe adding a more timid fish to an established tank where the fish get along is a bad idea? I know I'm pushing my fish capacity as well. Just wanted to hear some of your thoughts.

Quick parameter run down.

Salinity 1.024
Nitrates 15ppm
Ammonia nitrite 0
Ph around 8


Thank you.

 

[Subsea]

“Maybe adding a more timid fish to an established tank where the fish get along is a bad idea? I know I'm pushing my fish capacity as well. Just wanted to hear some of your thoughts.“

@gsw0716
That is the issue. Stop pushing the limit. It’s everything to do with established fish not allowing a timid intruder. Then on the other hand, you could add an aggressive fish and everybody else suffers.

Your choice.

PS; Consider adding diverse filter feeders or more corals. Fish Sociology & Phycology are complex.