sky high nitrate level????

[burrows14]

i have just completed my weekly water test on my biocube 29. everything was spot on except my nitrates were off the charts!!!!! i did a 25% percent water change last night and used R/O water like i always do. the only thing that has changed in my tank since my last test is that i have changed my light bulbs... help so my fishys and corals will look happy and be healthy again!!!!!!

thanks!
Ray