Need Help....!!!!

[eyeday]

hello guys
I just started my 45 g salt water fish tank about 2 months ago. I plan to put in the future some fish/corals in that tank. Now i only have 3 damsels which are doing great. I had a clown fish for almost 3 weeks and he just died. After the fish died i tested the water and the only problem i found was a low ph -- it was 7.....when the fish died, i didn't if know if that was because of the water quality. since i don't know a lot about this great hobby Ive been learning a lot from these forums but now..... IM SOO CONFUSED

and have a lot of questions
-What is the best filtration system for fish and corals?
-Do u know any good brand or protein skimmer that u'd recommend?
i want to upgrade my thank for a bigger one in the future (maybe 75g)
- What are the complete water tests that i need to do? when i went to the fish store they were asking me for alkalinity and some other tests that i didn't know. I have a test kit to test: Ammonia, Nitrite, Nitrate, PH
- Is important to have a refugium on my thank? what does it do?

 

[flower]

Wecome...
First, I think the damsels killed the clown...they kill everything including each other. Get rid of them, they grow up and will bite you every time you reach into the tank, drawing blood. They are pretty but evil.
Get a Marine MASTER Test kit...that is cheaper than buying each test individually. Calcium and Phosphate tests are what is missing from your list.
Filtration is a personal choice..I use canisters, no drilling and takes up less space, are easy to clean and come with a flow bar to move surface water which great...I don't need to point my expensive Koralia power heads toward the surface, but can use it rather to create flow for my coral.
I use a coralife skimmer...I heard octopus was the best brand.
A refugium is a very good thing...but it takes up space and it isn't necessary. It is just a quiet place where good critters like copepods can grow and multiply without fear of being eaten. If you keep critters like a mandarin a refugium is a must. They eat so many copepods and starve without them.

 

[crypt keeper]

I'd also take the damsels out. They will not allow you to have a peaceful community tank.
i would also add about 20 pounds of live rock. Some bigger 5 pound pieces if you can. This will fill the tank up and add hiding places for fish and allow corals to attach correctly to rocks.