Setting Up Brackish Figure-8 Tank

[MoonDancer]

I've had tanks in the past all freshwater set-ups and I've decided to get a bit more adventurous and put together a brackish tank. I fell in love with both Figure-8's and archer fish but decided to start smaller and see if brackish is my thing. So I'm looking for some tips from figure 8 owners before I set-up. I plan to stock the tank with at least one figure 8 and perhaps a small group of bumblebee gobies if anyone finds them compatible enough. I have done research, a lot in fact, but I find much of the available info is contradictory between websites so I thought I'd get info first hand from owners.

The things I have planned are:
The Tank - a 30 gallon hex (panels are 10" wide and 24" tall)
Brackish Water - approximate salinity 1.002 - 1.005
Stock - Figure 8's and Bumblebee Gobies

I want to know what any figure 8 owners are having the best luck with. Most places suggest sand substrates some argue it's terrible and to only use gravel. I'm leaning towards sand, are there better types or should I go with gravel? What kind of filter should I use as well? I'd prefer something quiet and want to avoid hang on back filters as the tank is quite tall and I imagine only half the water would be filtered well. With puffers eating habits I would figure you'd need a good filter to prevent excess debris. Is the planned salinity level good or do you have better luck with higher/lower levels? Will mature fish tolerate bumblebee gobies or will they be full out aggressive towards them? I'm not concerned about the occasional short chase, more so about anything that will cause the other fish to lose colour and be stressed out all the time. Also should I stick to one figure 8 or could I have two provided enough cover for the fish to duck in and out of? I want the fish to be comfortable and happy.

I really want to set this tank up well in advance for the fish and having as much info in my arsenal as possible. Any tips help. Thanks in advance.

[InvertPlanet]

your SG is spot on. It is nice to see someone doing their research before the purchase.

Sand vs gravel is more of a personal choice in this situation since neither the gobies nor the F8's are burrowers.

gravel is easier to deal with but, if you are going with live plants I'd go with sand.

[MoonDancer]

Thanks invert. I'll probably do sand as I'd like to opt for live plants if I can.

I've worked out some specifics now as well.
I'm opting for one single puffer now. LFS said I could house three but I doubted that from the get go. Between their size, possibility for aggression, messy eating habits, and low tolerance for nitrates/nitrites, one should be plenty to make that tank interesting and I'd rather prevent issues than try to fix them later. Also scrapping the gobies as a preventative measure. My tank bottom is probably too small for an adequate goby territory anyway. Essentially I've worked it down to a single specimen single species tank.