New to 3reef have a few questions

I have a 125 gal SW tank with a wet /dry filter system, with protein skimmer and recently added a 18 wt UV stailizer, also have 4 power heads. As of now the tank only has 5 fish just little damsels.
1st question is what is the best way to keep the sand clean?
2nd question is there any other items I might need or am lacking to make a better tank?
3rd where is the best place to buy SW fish online?
4th what would i need that i don't currently have to change over to a reef tank?
My main goal is to have the healthest tank possible, so I'm not killing fish by having a unhealthy tank.
Also if anyone has advice on care and maintance for a SW tank, I'd love to hear it.
Thanks for any info

 

Welcome to 3reef. A picture would help. 8)

 

The lighting I have 2- 30w Marine glo says there good for fish corals and inverts
and 2 -30w 11000K ultra daylight

 

how do you post a pic, never done that before.

 

What kind of lighting?

 

The best way to keep the sand clean is to by a fish or invert that stirs the sand. A diamond goby is a top quality sand mover and an easy and inexpensive fish to keep. Good water flow meaning as little dead spots in the tank as possible. 4 power heads is a good start. What size and type are they?
Make sure you have good water test kits and test regularly until your tank becomes stabile.
I dont use a UV sterilizer. There is good and bad to having one.
You did not mention that you have live rock. I am sure you have some but the more the better.
Do partial water changes weekly. Use only ro/di water.
As for becoming a reef tank start with the easier things first and work you way up to the harder corals to keep. Zoas mushrooms leathers. Keep in mind when picking your fish that some angels will nip at corals and may cause future problems. Study the fish you are considering and make sure they will get along. An angry and jumpy tank is not a fun to look at as one that everyone gets along in.

 

That lighting is not good enough for a tank your size to keep any corals except possibly some mushrooms. It is good enough for a fish only tank though. So as your budget allows, plan for quality future lighting either T5s or Metal halides or both. If you get pcs only you will be limited in what corals you can keep.