Personally, I see two reasons for water changes:
1. Removal of pollutants from the water.
2. Nutrient replenishment.
I believe what we're speaking of is Dutch Synthetic Reefing. As I understand DSR, ( please correct me if I am saying something wrong or inaccurate), the idea behind this method is uber filtration combined with nutrient replenishment. No water changes, only the replacement of what's lost through evaporation.
I am running DSR on my nano reef.
Yes, strong filtration and adequate flow are essential components, as they should be in any reef. The skimmer removes a lot. A powerfilter is also used to remove detritus after blasting the rocks and sand.
However, the key to DSR, as I see it, is full conscious control over the main parameters, testing the main (generally agreed, at least anecdotally) factors for coral growth (Calcium, Alkalinity, Magnesium, Strontium, Nitrate, Phosphate, Iron, Potassium, Boron and Iodide) and maintaining these levels as stable as possible. This is done by dosing pumps usually but some DSR members use a calcium reactor in combination or dose manually. Nitrate is dosed if nitrate is low until nitrate can be maintained at 2.5ppm. Phosphate is dosed until it can be maintained at 0.04ppm. If either of these nutrients get too high, then an iron-citrate mix is dosed periodically to precipitate phosphate (similar to lanthanum). The phosphate precipitate is then removed by the powerfilter or the skimmer. Nitrate is reduced by ramping up the dose of a vinegar-sugar mix. Eventually you can find a happy dosing regime that maintains all the nutrients at desired levels, but you have to test and adapt to figure that out.
In addition, as DSR allows you to make your own salt mix using analytical-grade chemicals with as litte impurity as possible, you can correct your water with an emergency water change or a reset should you need to. One example might be if you do an ICP test and you notice your sulfate-chloride ratio is off (whether that has any effect is moot), you can then correct that with ease. Another example, if your magnesium is too high due to an overdose, you can do a water change with your own salt mix that has the other main parameters actually matching your current water (because you have just tested these), but that is lower in magnesium to bring that element down. Another interesting note is that under DSR, you can keep salinity at 33ppt but maintain the other main factors to be at the desired levels. So there is less osmotic stress on the fish but the corals still get what they need.
For the most part, wet skimming and giving frags away because they're growing too fast is all the water changing that is required.
You can occassionally run carbon or GFO should you ever need to - the rules are not set in stone. I dose DIY KZ coral snow to improve clarity.
It is really quite an easy way of reefing, and it is certainly more economical on a larger tank. On my nano (100L tank), it's about even in terms of cost when comparing DSR with weekly 10-20% water changes, but I enjoy the testing and the learning and tweaking and the conscious control. In terms of effort, it is mostly automated. Obviously basic maintenance tasks cannot be avoided, such as cleaning the glass and emptying the skimmer, but it does make things nice and stable.
DSR differs from Triton in that:
- there is no algae bed,
- you can use UV and ozone if you want,
- you can use a zeolite reactor to provide bacterioplankton,
- there is no need for ICP testing (but you can do it if you want), rather you use tried and tested hobby-grade kits that are accurate enough and allow you to take immediate corrective action (not waiting a week for an ICP result),
- it does not target NSW values but rather tries to find the target values that grow corals best.
Both Triton and DSR chase (and seem to achieve) the same goal (a thriving reef tank), I believe, but they approach it in slightly different ways. I see the Triton method as an ecosystem approach akin to organic farming with conscious control as far as possible. This requires more sump space and is, in my opinion, much more dynamic because it is such a holistic approach. Whether this dynamic ecosystem approach makes it harder to intervene and isolate cause and effect is something I am unsure about. I see DSR as a simple garden (with a weed mat) that is more manageable and a little less dynamic as I have slightly more granular control over the main parameters (rather than using four secret mixes that often end up needing to be supplemented with the main parameters separately because of different consumption rates in different tanks.
