Posted by: BrianC I have to disagree with you Michael V. Water changes are likely the best nutrient exporter. The reason we use all these other mechanisms is on the larger tanks water changes can get really expensive... I think all these mechanisms work to some degree. Problem is they really are only about 80-90% efficient and nothing is ever going to get 100% - short of starting with new RODI saltwater.We know what new water means - starting the nitrogen cycle all over again - it shouldn't be the goal.For example I see in a lot of advanced tanks almost no remaining clean up crew - I see the remnants where they once were and maybe a turbo snail or a hermit. There isn't enough algae (food) to sustain them. Which I think if you look at the fauna in a DSB there isn't much there either. We teach or are taught fresh water has high nutrients whereas Marine Environments are "sterile" - which we all know nowadays is not true. It is simply the Marine Environment is huge and everything is fighting for those limited nutrients. There are studies that show corals (some) grow more rapidly in nutrient saturated environments - hence nitrate and calcium dosing. We don't want an environment with 20ppm ammonia. We want an environment with .0000001ppm ammonia. Where our environment is so kickass at eating the ammonia it's hard to find. Sulfur occurs naturally in a marine environment from the decomposition of organisms. We get rid of it with high water flow. Sulfur can create a lot of really bad stuff in your tank. Problem with bioballs etc is eventually they will store minerals and nutrients (sulfur or something similar) In my opinion closed environments are ALWAY bad. I can easily take an algae scrubber remove the algae discard it and add it back... It's also cheap! said:
I would call water changes a good nutrient exporter, possibly the most efficient from an electrical perspective, but not from a functional perspective. I was recently dealing with a bacterial bloom (I probably have a higher nutrient tank than many, but I also have zero nitrates and phosphates). Didn't have UV handy, but carbon/Purigen wasn't doing anything. I also connected it to a 600 gallon system (200-250 in the original display) that was recently filled, so in effect had a large water change. Fought it for a couple weeks, then finally upped my fuge lighting a bit. Problem solved in 48 hours.I agree that bioballs aren't good for much, but not because they trap nutrients. I see bioballs as a low efficiency version of a foam block, or live rock depending on how you want to look at it. Old live rock (and old sand beds that haven't been cleaned) have all sorts of gunk in them, just like bioballs. Routinely keeping the system clean (export method of your choice) is the only way to cut down on that, and will also work for a bioball system.One thing a water change does do very well is bring water parameters (Ca, alk, Mg, trace, whatever) to the correct value. Too high and they lower it, too low and they raise it (assuming good source water).
