There's no doubt that 80 ppm of nitrate is high for some systems... BUT... If everything is happy and you don't have algae problems, don't change too much just to lower them.
Several big (50%) water changes in a row can reduce nitrates that have slowly climbed to a high level. The first will reduce ~80 ppm to ~40, the second to ~20 ppm, and etc.. If that doesn't work, you either have nitrogen compounds in the new water or a bad test kit. Remember, nitrite can cause elevated readings on nitrate test kits. Once lowered, & without some addition reduction mechanism, nitrates will just climb back up over time.
Once you get the level down, more porous rock, something like Matrix Blocks, or maybe a sulfur denitrator might help maintain the levels if you don't have measurable phosphate levels using a quality test kit. Carbon dosing, algae turf scrubbers, & Cheato can do the job if you have measurable phosphates. I didn't see any mention of skimming. That can slow the build-up of nitrate also.
Several big (50%) water changes in a row can reduce nitrates that have slowly climbed to a high level. The first will reduce ~80 ppm to ~40, the second to ~20 ppm, and etc.. If that doesn't work, you either have nitrogen compounds in the new water or a bad test kit. Remember, nitrite can cause elevated readings on nitrate test kits. Once lowered, & without some addition reduction mechanism, nitrates will just climb back up over time.
Once you get the level down, more porous rock, something like Matrix Blocks, or maybe a sulfur denitrator might help maintain the levels if you don't have measurable phosphate levels using a quality test kit. Carbon dosing, algae turf scrubbers, & Cheato can do the job if you have measurable phosphates. I didn't see any mention of skimming. That can slow the build-up of nitrate also.
