Random Cyano outbreak?

[cor4eyh]

I have a 50 gal cube with 16 gallon sump all has been fine and then randomly I have this massive cyan outbreak. I noticed a couple of fish gone but after much digging I found no bodies or bones. Also my snails seem to be dieing off aswell. Now I don't normally test and I know most say you must but I only test when somethings wrong. So my test results are as follows nitrate .03 nitrite .00 phos .02 no ammonia I'm waterchanging every week until futherado any advice or info. please let me know :)

 

[Reefing Madness]

If you've got snails dieing off, those babies cause water issues, big time. Fish are usually taken care of via CUC, but the snails for some reason mess up the water.