Greetings All,
We are new to the reef tank hobby. We purchased a 3 year old fish only system a year ago. Over a few months we worked on lowering nitrate levels in order to add corals. We were able to get nitrate levels below 10 reliably and acquired several varieties of coral, mushrooms, ricordia, candy canes and colt corals. The tank was kept stable because we gave it a lot of attention and anytime something seemed "off" we worked on correcting it before it got out of control, so problem solving experience is minimal.
We had to leave town on business for 5 months. We had a professional recommended by a local fish store maintain the system. He came by every other week to do water changes (if needed) and clean filters etc. We left detailed instructions for the house sitter for daily tasks.
We returned to find 2 fish had died, several corals were gone, and there is green hair algae all over. There was also tiny hard pellets of something covering the refugium and display glass. Most of the snails, emerald and hermit crabs are also gone (we had a clean up crew.)
Testing the parameters we found this:
salinity 1.027
Nitrate 10
Ammonia <. 025
Kh 9.9
ALK 3.53
Ca 430
Mg 640
The Mg and ALK appear to be way off. I'm guessing (please correct me!) the hard pellets are precipitated calcium.
I started by cleaning all filters and getting the biopellet reactor going again (had clogged with debris and stopped). I was told a water change had been done the day before we came home so have not done another yet.
Clearly the chemistry must also be addressed but I am in over my head.
Any advice would be greatly appreciated.
Thank you for taking the time to read through this.
We are new to the reef tank hobby. We purchased a 3 year old fish only system a year ago. Over a few months we worked on lowering nitrate levels in order to add corals. We were able to get nitrate levels below 10 reliably and acquired several varieties of coral, mushrooms, ricordia, candy canes and colt corals. The tank was kept stable because we gave it a lot of attention and anytime something seemed "off" we worked on correcting it before it got out of control, so problem solving experience is minimal.
We had to leave town on business for 5 months. We had a professional recommended by a local fish store maintain the system. He came by every other week to do water changes (if needed) and clean filters etc. We left detailed instructions for the house sitter for daily tasks.
We returned to find 2 fish had died, several corals were gone, and there is green hair algae all over. There was also tiny hard pellets of something covering the refugium and display glass. Most of the snails, emerald and hermit crabs are also gone (we had a clean up crew.)
Testing the parameters we found this:
salinity 1.027
Nitrate 10
Ammonia <. 025
Kh 9.9
ALK 3.53
Ca 430
Mg 640
The Mg and ALK appear to be way off. I'm guessing (please correct me!) the hard pellets are precipitated calcium.
I started by cleaning all filters and getting the biopellet reactor going again (had clogged with debris and stopped). I was told a water change had been done the day before we came home so have not done another yet.
Clearly the chemistry must also be addressed but I am in over my head.
Any advice would be greatly appreciated.
Thank you for taking the time to read through this.
I agree with Pete, you don't need a phosphate test to tell you that you have phosphate since you have an abundance of hair algae. I also agree that a couple of large water changes (maybe three days apart) can help replenish your levels that are out of whack. If it were me, I'd take out the rocks and scrub them and also use a little hydrogen peroxide on them outside of the tank and then place back into - I would do this over time and not all at once. I've used 3% hydrogen peroxide and after scrubbing as much as a I could off, I put the peroxide right on the algae (not the corals - you'll have to submerge your corals while doing this or remove them from the rock) wait 10 minutes and then put back in the tank. The algae will slowly fade away. I would then run some phosguard (if you don't have a reactor) or GFO in between your water changes. Definitely get your membranes refreshed before doing any large water changes. 
