Quote:
Originally Posted by Vancity
(Post 856650)
Sorry for the delayed specifics, had a busy weekend
I was actually referring to WC's to reduce nitrates and phosphates VS reactors using GFO, carbon, bio pellets/balls etc... Taking care of Mag/Alk/Cal are dosed using Magnesion and C Balance part A+B (thats the extent of my dosing done). The tank uses a refugium, skimmer and filter socks currently to reduce bio load, and i don't run GFO. Until mrhasan touched on calcium reactors i hadn't done any research into them to know what they were even used for. Since reading up on them they make sense! Just not sure if they're worth the cost setup and space VS using dosing pumps + C Balance, we'll see.
So far it seems no matter how many setups i've seen with hundreds or thousands of dollars in equipment over and above what i have, people still do WC's from 5-100%. Auto water change systems such as the Genesis appear to accomplish the most of what i'm looking for, space however is the issue
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It all depends on what your nutrient loads are like. If you've got a heavily stocked tank that you feed a lot, there's a good chance that your tank is going to producing quite a bit of nitrate and phosphate. Depending on what inverts you want to keep, you may or may not be able to keep up with it just by doing water changes alone.
For example, if you've say got 20ppm nitrate and you do a 20% water change, you're nitrates are only going to fall 4ppm to 16ppm, which is not really that big of a drop. It will be tank specific, but let's think about a hypothetical situation in which your tank is heavily stocked and well fed, you've not got much by ways of denitrification happening naturally in your rocks or sand and you've got no nutrient export system other than a skimmer. It's not unfeasible that in a week, your nitrates could rise 8-10ppm. If you're only doing 20% water changes once per week, and on week 1 you had 20ppm nitrate, you'd do a water change, and by week two you'd have 24-26ppm. You'd do another water change, and by week three you'd have 28ishppm nitrate. This situation would either require much larger volumes of changed water, or more frequent water changes, which quickly becomes burdensome and inefficient.
The only time in which nitrate and phosphate control is feasible through only water changes long term is when their percentage increase in the water column in the time between water changes is less than the percentage of water that you change, and it is very difficult to gauge whether you're actually doing that or not because...
As tanks mature, nutrient cycles in them become ever more complicated, so the actual amount of 'nitrate' and 'phosphate' (as in biologically available nitrogen and phosphorous) that is accumulating in your system may not remain dissolved in the water column and visible to your tests. Algae and cyanobacteria are very efficient at drawing available nutrients from the water column, so it's entirely possible for you to find yourself in a position where it appears that the concentration of nitrate and phosphate in your water column is staying stable (or undetectable) week over week - implying that water changes alone are enough to control for those nutrients - and yet you've got uncontrolled, luxuriant growth of problem algae that are outcompeting your corals for light and space and directly stunting them through allelopathy. If you find you've developed such a nutrient regime, you can do all the water changes you want and it won't really help because your nutrients aren't actually in the water column, they're being efficiently captured and recycled by unwanted biomass. Those situations can be extremely difficult to break out of because they're a fairly resilient ecological state.
It's for that reason that I maintain some other permanently running method for dealing with nutrients in my tank. In my case it's GFO and biopellets that are acting as active competitors for nutrients as they become available in the water column 24/7, and not letting them accumulate over the course of a week waiting for me to physically suck them out.
I still do large water changes because there's other important parameters that can drift over time, some that I test for, some that I don't, and the easiest way to get them back to where I want them is to simply replace the water.
ETA: Additionally to the example above, if all you were doing to maintain nutrient levels was a 20% water change every week and your tank was adding approx 10ppm nitrate to the water column every week, your nitrate levels would drift up until stabilizing around 50ppm assuming you never missed a water change. Depending on the tank, that might be a perfectly acceptable scenario.