[DoLceNBeLLa]

In regards to the goby, some gobies only eat by sifting through live sand in their mouths. That might have been the problem if you didnt have enough sand or it wasn't filled with enough stuff.

I have one of those pseudochromis fish in my 55 gallon and it still picks on my yellow tail damsel like mad. Try switching it for a neon goby or something that is smaller and less likely to pick on the other animals.

In general it sounds like you're rushing your tank's capacity a little. If you look on some of the other forums here, people have threads going for months as they set up their tank. Try keeping the tank as is for a month with regular water changes, maintenance etc. If everything is looking great then move forward.

Sorry for the losses and good luck!