Also a FTS would prob go along way in getting the best advice.Like @eatbreakfast said they will certainly take the fish back they may not give you anything in return but is the money you lose worth the fish life? That is the question you have to ask yourself. Also You said other fish...what other fish are we taking about? Ok for everyone who is in this thread I think we all want a major rundown of your 55gallon tank before we can help you further. It seems every time you reply their is a new surprise such as "other fish". Please list the following ASAP: Ammonia,Nitrate,Nitrite,Salinity, tank size,does it have a sump,Every fish and #, do you have a clean up crew,if so what does it consist of, do you have a skimmer,lighting,any other living organisms, has this tank had any diseases in it from the past 72 days? Some of these questions have been answered but I would like all this info in one post so that we can get a basic understanding of you entire system. DO NOT Leave any important info out and other info you would think would be beneficial please share it. lets work this thing out. And you said it yourself restarting is probably the best option. So is the only thing holding you back from the restart the fish? Lets get you back on track, Im willing to work with you but you gotta not shrug good advice off!