Hi...this tank looks very familiar to me...:flower:
Welcome to MR and im personally glad to see you joined this great community.
Now to the Q/A.
I will try to start from what i think is important right now at the most
I know that this tank was set up for only few weeks and this is time when your tank is going through the process called cycling...please search some threads on the CYCLING to understand the process better
Before you get to decide where to spend your money you need to research several vital requirements for keeping a salt water aquarium...
this will include topics on:
1.FLOW in your tank VS tank SIZE (research the type of the saltwater tank you would like to keep and required FLOW/Equipment you need)
2. LIGHTING for the environment you would like to keep( fish only, mixed reef, softy tank LPS tank, SPS reef etc)
3.Marine chemistry. (no need to get scared, you need to understand when to make water changes and see if anything wrong with the tank
With all that i trying to say that you need to relax and enjoy this SLOWLY, bit by bit gathering information, while you new tank is cycling(6 month!!!!!!!) and you have time to read and pick your plan
Good luck
Greg