I have a 55 gallon salt water aquarium. The tank was up and established for about 8 years with no major issues to speak of. I had to leave town for around a year due to work and the left the care of my tank to a family member. This is where the fun starts within 3 months the tank crashed. Upon returning home I found the tank to be about 15 gallons low of water with some of the live rock exposed (dead).
The tank has approximately 100lbs of live rock some of which appears to be dead.
Sand bed is about 2 inches and around 8 - 9 years old.
I have done small WCs and attempted to get things back in order for the past two months give or take. I have been dosing frytzyme 460 a normal regimen of Kent Marine additives as well as running carbon and a nitrogen sponge. Which does not appear to bring down the nitrates at all.
So, water changes of 30 gallons have been done daily for two days with zero affect.
The folks at my LFS are recommending that I change out the sand bed and I am considering it but wanted to ask some of the experts here with more experience in this hobby for any advice you may have to identifying the source of the problem.
If it was your tank how would you handle the situation ?