personally, and backed up with this forum, bumblebee gobies are freshwater, ive kept them in freshwater for years and had no effects.amano shrimps are not brackish, again ive kept these algea eating shrimps in my freshwater and lives for a good amount of time.Malaysian Trumpet Snails are freshwater, not sure if they can survive in brackish, as salt is bad for most snails, but i wouldnt try it.the same with nerite snails?and with the endlers, i wouldnt bother, they are freshwater and why put them in brackish.i havent kept crabs so cant comment.
again, backed up with reliable sources, i think figure 8's are freshwater. they do orginate from Freshwaters of Southeast Asia. they grow to app. 2.5 inches (6cm) and changing my mind from eariler, 1 would be best. they can live together but need the room. im not saying they cant live in pairs in a 7.5 g, provide lots of cover and hiding places, but looking at my 10 gallon that i have 2 in its smaller than i first thought.1 wont get too big for a 7.5 gallon i think.try looking on google for extra help and info to make your mind up. i started out with just 1 puffer a while back and fell in love with them ever since. but its up to you, just giving my opinion
