If water quality has gotten a bit off, do water changes its the cheapest way to get things back in line. if you have sensitive corals do smaller changes. for example

my 500 gallon system had 50 ppm n03, other wise was perfect. I did two 50% water changes with new SW "REEF CRYSTALS " water that matched my parameters at this time, expect the n03 of course. I'll add that i had a horrible cloudy issue with both batches. but that mix was closest to my current tank parameters ALK n CA wise. id have chosen Red sea mix if i had to do it over again. and my corals tank was isolated for several hours while everything mixed and then i slowly mixed the new system water into he over all system. this is because enthuse system i have an attack d 60 gallon frag tank I'm growing out in. the main display doesnt have any sensitive corals so any parameters shock, which was only less n03 all of a sudden anyway, wasn't an issue. i am seeing a influx of new algae in the coral tank two weeks later due to stability and red field ratio ill not get into that. its nothing my tang can't manage. just something i noted. maybe due to something in the reef crystals mix.

SOOOOO were back in line at 10 ppm n03 which is where i want mine. bio pellets can take months so stabiles and do there job. there more of a long term maintenance product IMO. start with good water quality and choose your method to maintain it.

Be it water changes.. or bio pellets or carbon dosing with vodka. back to the point, when things get off, do extra water changes because it works. its not a guess or a partial fix its bring s everything back inline.

ill second the aptaisa X stuff. it works well and does little damage to other things in the process. other wise it can be a complete tear down some times to get them gone gone. they don't need light to survive.