help with a question

Let me first start off that I am new to the forum and the saltwater fish hobby. The problem is that I keep losing fish. My tank is about 6 mos old. It is a 56 gal fish only tank. The params have always been good. Since the beginning I have gone through two clowns (one at a time), a royal gramma, two yellow tail damsels (one at a time), two yellow tangs (one at a time), and a six line wrasse.
There have been no real issues with the system or parameters. No ick, etc. I have two airstones. I feed ocean reef flakes and marine cuisine frozen food. I do the garlic extreme with the food and water changes about once a month. I do not have a protein skimmer yet. Temp is 79 F.
I have had a firefish and coral beauty in since the tank was about one month. They are both healthy and get along with the other fish that are introduced.
I just don't get what's happening. For instance, my latest clown got disinterested in food over the last week. He would only eat the flakes and would would just seem sluggish. His color was fading. Yesterday he didn't eat at all and seemed to stay on the bottom. This happened with my last clown. My wrasse was fine and had no problem eating. Today, I find the wrasse dead and clown dying. The only thing I did yesterday was add maintenance buffer. The pH was 8.4. Today the pH is 8.4. Everything else is 0. Salinity is fine.
What the f___ is going on? I'm stumped.
--Rob

 

Ok, well... lets start with the basics. Since you state you are new, lets double check all your levels.

Temperature
Salinity
Ammonia
Nitrate
Nitrite

These are your basic tests for a FO (fish only) tank.

 

Temp is 79 F
Salinity 1.022
Ammonia 0
Nitrate 0
Nitrite 0
I forgot to say that the latest two casualties were in the tank for at least three weeks. Also, I use tap water (hmmmm).

 

None of your levels are anything to worry about. I personally would raise your Salinity up a little, but it is good enough for fish.

What do you have for water movement? Do you have any surface agitation?

 

Did you get all your fish from the same place?

 

Got the coral beauty and one of the tangs at a different place. Rest of fish bought at local chain pet store. This includes the firefish that is doing fine today.

 

I would wonder about the health of the fish at the store, since your water seems fine.

 

This could be the case,but you should list everything about your tank so everyone here could help you best..h2o params,filtration,meds/chemicals/test kits used(with expiration dates)/acclimation used...I know you posted some stuff already but go over it and test again sometimes they differ..

 

Tap water is not a good idea for a saltwater system. Too many variables and too little consistency.
What do you have for filtration, aeration and movement or circulation? Saltwater fish demand high dissolved oxygen so the water needs to be moving constantly and surface agitation is very good as it gives you greater contact with oxygen.
Do you have the latest water quality report from your water provider? Do you know if they use chloramines or any alternative disinfection methods? Do they feed phosphates for corrosion control in the distribution system? As I said before there are too many unknowns or variables with tap water and I am a Plant Supervisor by profession. I woundn't hesitate to drink it but I will not put it in my aquariums.

 

I'm thinking it might be the water, too. I use an Eheim canister filter. I have two six inch air stones. Another factor is that my circulation is nill. What should get for circulation? I tried powerheads, but they are too powerful for the tank.