How much are you feeding the fish? How long are your light cycles? Are you using RO
can be the result of many things. Overfeeding is one, too much light is the other, and there are certain chemicals/elements in tap water that will allow cyano
to ravage your tank, which is why RO
water is recommended. It get's rid of 99% of sediments and trace elements like nitrates, silicates, etc.. All the things that could easily make a nice saltwater tank turn disgusting.
Also, doing water changes will only slow the cycle down unfortunately, and it will take longer to complete. Honestly, since you only have one fish, why not bring it back? Don't even ask for money or credit.. just give it back. That's what i did for some of my livestock when i couldn't afford to support them anymore. If you get rid of the fish, you won't have to do PWC
's and your cycle will most likely go much faster.
Sorry to the fact that you found out your LFS
is shady. Most are, and most people notice this AFTER they've been had. It's a sad story.