I am new to this hobby. I started a 36 gallon (tall) FO tank, Penn-Plax 1000 canister filter, 18w lamp, Tetra air pump providing bubbles through my barnacle. Submersible heater, Aragonite substrate about an inch thick.

Current Water Conditions:
ph 8.3
Ammonia .25ppm
Nitrite 0ppm
Nitrate 0ppm
Temp 75.5
S.G 1.022

Every time I add a fish they die. The first two I added (domino damsels), one of them died the next day and the other died 3 days later. I had the water tested and tests showed that my ph was too low so I purchased Seachem Marine buffer and slowly brought my ph up over several days. I have checked my filter for clogs that might slow down filtration, I have tested the water myself and taken water samples into two fish stores and both have confirmed that my water conditions are now suitable for fish. At the time I purchased my first two fish I also purchased two Nass. Snails and three Blue Leg Reef crabs. My inverts are doing very well. I went to the local fish store and talked to the owner who tested my water and everything was good. He suggested getting one more fish (domino damsel) and see if anything has changed. That fish died over night. I dont want to kill anymore fish!

I purchased the tank used. I cleaned it out well with fresh water, I used "Seachem Prime" to neutralize any chlorine or metals that might be in the tap. I mixed the salt in the tank and then waited till the next day to add my substrate and decor. Then I waited about a week, adding "Seachem Stability", based on the instructions, to my water to help start the bio-filter. Im not sure If I have done something wrong here but I cant keep my fish ALIVE! could there be some other contaminant in my water? is there a way to test for foreign contaminants? PLEASE HELP ME!

Your salinity levels are a little low. Usually you want it to be about 1.024-1.026, but I don't think it is low enough to kill a fish. I had my tank up to 1.028 (on accident, I mixed my saltwater to salty somehow) and it didn't kill anything. So I doubt that is the issue. Your ammonia could be better, but really, I think that that low of a level wouldn't really bother some domino damsels.
Unfortunately, there isn't really a way to test for other contaminants. If you are planning on corals though, I would recommend using distilled water or RO or RO/DI water. The Seachem Prime probably takes out most of the crap in the tap water, but maybe there is something else. I would look into buying an RO system, but if that isn't an option (like with me), I would ask at your local fish store. Some sell RO water or saltwater that is pre-mixed. My LFS actually gives away RO water for free, and they sell saltwater for like $0.15 per gallon. Another option is to use distilled water. You can buy it by the gallon at most grocery stores.
Once again, I don't think that a little chlorine or whatever may be in the tap water would bug a damsel.
I'm pretty sure of this but just checking...you use the Seachem Prime on all of your water you put in the tank right?
Also, not to say that you should change it, but sometimes canister filters can become a problem over time and become a factory for nitrates, ammonia, etc. In fact, you don't even need any mechanical filtration. I am running my 12 gallon nano cube dx with no mechanical filtration, and I have 2 fish, a clean up crew, shrimp, and a lot of corals and it is fine. Mechanical filtration can become a problem, because it catches the junk, but then if you don't clean it out a lot, it will start to decompose and produce ammonia and stuff. Not to say that mechanical filtration is always a bad thing, because a lot of people use it in their tanks, you just have to stay on top of it.

Your salinity is on the low end of ok. You'll need to bring it up if you want to keep coral and healthy fish though. How much live rock do you have in the tank? Do you have powerheads for the water flow or just a canister filter? If all you have is the canister filter, you may not have enough oxygen exchange to keep your fish alive. Is your tank covered? this will also decrease oxygen exchange. Your levels look ok but the ammonia shouldnt ever get higher than it is. How long have you had the tank running? Your temperature is a low also. Keep it at 78, if it fluctuates below what you have it, it could be too cold for the fish.

Sorry for all the questions.. it'll just help us to know what you have to help pinpoint the problem.

Ok. So I will raise the temp a bit and see how my inverts do. I will also raise the salinity but my LFS owner told me that I should never raise it to 1.026. There seems to be so many opinions on proper water conditions its so confusing for a newbie. I have NO live rock or sand because another thread I read said that if my water perimeters weren't right that the live rock would die. Is that true or should I consider getting some and how much? I think my Oxygen exchange should be good since I have the top open, the outlet for the filter churns the water at the top and I can see bubbles mixing around, and I have an airline pumping bubbles through a cluster of barnacles. I currently dont have a powerhead but am considering one. I use tap water to top off my tank and then add the Prime to it when it is topped off, but I haven't added tap water without the seachem when I've had fish. I am thinking about waiting a few more weeks before I add more fish to see if after it has completed cycling, the fish are able to survive. thanks for the suggestions. I welcome any more that you may have

So here's the problems i see with what you have going.. these are just from what i know though:
The salinity should be between 1.021-1.026. if you have a reef aquarium with fish, a good number to shoot for it 1.024. 1.022 is too low for coral to thrive in but fish can withstand a slightly better range. Yes, above 1.026 can be bad in the long run so dont go above that.
You NEED live rock in your tank. This is the main method of filtration in a reef/fish aquarium unless you have a massive filtration system with a ton of maintenance. Live rock is the basis for the bacteria to grow on that gets rid of the ammonia, nitrites, and nitrates in the tank. It works the same way (in a different manner) as the bacteria in a freshwater tank. Your live rock will die anyway. Since it has been transported from the ocean to the store to your tank, a lot of stuff will die off but the stuff left will take over. That's why you must "cure" the live rock for a few weeks. This gets rid of the dead matter and the bacteria will start to reproduce on the rock as well as some small inverts, corals, and algae. You need at least 1 pound per gallon of live rock for your tank. The same goes for the sand in almost every way. Except, if you get crushed coral/sand, it'll help buffer the ph in your tank.
Tap water can be bad for a salt water tank. There are a lot of heavy metals, chlorine, and other stuff that can cause havoc on your life forms. So if you can, get some R/O water from a LFS and either get it premixed or get some salt water mix to do at home. Also, never add calcium, salt, or anything else to your tank if its not premixed with water. This can harm the life in your tank. I think it's 1-1.5 cups of ocean salt (not regular salt or aquarium salt for fw setups) per gallon of water.
You'll have to get 1 or 2 power heads for your tank. You'll need to have a good water flow around your live rock and also so you can imitate the fish's natural habitat. They live in the ocean which is always churning and moving around. For your tank, plan for at least 20xgallon for a good flow. So for a 20 gallon, you'd need at least 400 gph flow rate around your tank. More is good though.
The easiest way to know if something is correct or not in setting up any aquarium is to look at the natural habitat of the lifeforms you're putting in it. If you have coral, then you'll notice they live in somwhat shallow water (5-30 meters of water that gets moved around all the time) with bright sun (its in the tropical regions of the world), and fairly warm temperatures (about 78 is average) with bacteria and other lifeforms evolved to eat the left over foods and stuff from the lifeforms higher on the food chain. If you're missing any of this, then you're not there quite yet.
Hope this helps!

I really appreciate all the response. I raised my temp slightly last night to bring the temp just under 78. I will look into the live rock but it's so crazy expensive especially for 36 pounds, lol. I will work today to raise my S.G and then work on an RO system. Ill update this post again once I have reached the parameters you all have suggested. thanks again

1.) stop adding water conditioners.

2.) add macros algaes like chaetomorphia (brillo pad) and caulerpa profilera.

3.) let the tank run for a week to estabilish the macro algae.

4.) add a male molly slowly aclimated from fw to salt.

5.) don't add food for a week.

6.) start feeding 1 flake per day.

7.) wait 1 week.

8.) then try a couple marine fish.


just my .02

__________________
fw leiden since 1979, fo salt since 1979, mixed reef 55g 2002-2009. Strong emphasis on the tank taking care of itself. Balanced with plant life, no water changes, tap water, no filters in FW. Only dosing calcium, alk, mag in marine reef tanks. http://www.aquariumforum.com/f15/my-...ods-26410.html
recent tanks (till 2009) 7 years- 10g FW leiden 7 yrs, 55g mixed reef 7, 2 yrs, 20g FW leiden, 10 g fw leiden , 29g mixed reef, current tank 55g leiden

Phys and beaslbob are right.
You definately need live rock and sand. It is expensive, but if you think about it, it is pretty much what will keep your tank going in the long run.

If you want to wait, it is possible to get live rock as you go. But you wont be able to get fish or coral because every time you add some, you have to cure it. It is possible though.

Unless you buy cured live rock.

since the cured live rock will be changing tanks, parameters will be different and potentially cause another die off.. so you will still have to watch for the cycle.. but it will be quick if you see one at all.

yeah, thats true. but if you are careful there will be a minimal die off. One thing you could do is do a water change or something, and then put the live rock in that water on the way home, so it would be in water the whole way, then put it straight in your tank, but chances are there would still be a little die off.