#violet goby

Im thinking about getting one of these guys in the future. Its not in the budget right now and I'll be moving out of state and already have two Bettas to transport.

I was in Wal-Mart a while ago and saw a few of these guys hanging out and fell in love. I knew i needed to get one eventually and with me and my boyfriend moving and building our own house i figured, why not make plans for an aquarium thats big enough to accommodate one of these guys?

I do need things to be cleared up for me though so i can get the ball rolling.

Tank Size:

Ive read a lot of different things, some places say 50 gallons per goby others say 48 inches of tank and some say 50 inches. Hunting down a tank based solely on inches is a nightmare. What size tank do i need in an easy plain speak? Recommendations are welcome of course and appreciated.

Substrate:

Ive heard that sand is what is supposed to be used. Would a sand/gravel mix be fine or should it just be straight up sand?

Water:

I understand that they are a brackish fish and need brackish water to live comfortable, long, healthy lives. I plan on doing more research into this but i am kind of confused right off the bat. I had heard that any salt added to an aquarium would eventually be filtered out by the filter and that was why you shouldnt run a filter when treating fin rot. In short, any resources or information anybody has to point me in the right direction is very much appreciated.

Plant:

Are plants possible? Ive heard people say yes and ive heard people say no due to the salt. I like planted aquariums because of how natural and covered they look. Are there any plants that would survive in those waters or is that a no?

As far as water temperture goes I can do that, that may be the only thing that actually makes crystal clear sense to me.