Some aspect of it's (limited) use, hhmmm so what's the Pros vs. Cons I'd like to know .... :hammer:
" "¢ Monitors salinity via a standard conductivity probe.
"¢ Monitors pH via a standard pH probe.
"¢ Monitors ORP via a standard ORP probe.
"¢ Monitors the sump's water level and adds top-off water as necessary. (The Dialyseas unit normally adds RO/DI water for top-off. I feed this RO/DI water line into an electronically actuated three-way solenoid valve that splits the RO/DI flow between the sump and a Nilsen (Ca(OH)2) reactor. The solenoid is controlled by an Aquacontroller, and is responsive to the tank's pH. If the tank's pH is > 8.4, the RO/DI top-off water goes directly into the sump. If the tank's pH is < 8.4, the RO/DI Dialyseas output is used as the Nilsen reactor's input, and Ca(OH)2 solution is infused into the sump instead.)
"¢ Dialyzes aquarium water at the rate of 1 gpd, or about 18% of the system's total water volume per month (for the reasoning behind my choice of this value, and for a convenient way to calculate your system's water volume, read on!)
"¢ Adds concentrated salt solution to replenish salt removed by dialysis. This function is THE single critical feature that defines success or failure for the whole Dialyseas concept. Questions of salt quality, the feasibility (or not) of maintaining a reasonable salt composition in a "concentrated salt solution," and salt solution delivery mechanics all come into play when analyzing the Dialyseas' performance on this pivotal point, as discussed in detail below."
Paul
I assume you are listing the above points as pros?
The unit does not appear to be a controller by your description. It is only capable of monitoring (not controlling) PH. It does not activate any device to raise or lower the PH value as needed. I see the author has incorporated a separate controller and Nilson reactor (used for mixing RO/DI source water with calcium hydroxide to raise the calcium level and PH). These are all features that run independent of the Dailyseas unit and appear to only use the product RO/DI water line from the unit. A Nilsen reactor will raise the PH quickly if it isn't set-up properly, but it isn't a device one would use specifically to raise PH, as it would do so for only a short period of time and add a disproportionate amount of calcium in doing so. Sodium carbonate would be a safer way to raise PH, but once again it must be buffered with sodium bicarbonate (which will lower PH), calcium and magnesium to maintain an ionic balance.
The unit monitors (not controls) salinity, but likely adds the stock solution according to the volume of water processed, rather than the actual values of each individual salt in your water. It monitors ORP, but unlike a controller, it doesn't govern an ozone generator capable of raising it. It's capable of topping off the sump but I doubt it has the many fail safes of a dedicated top-off system such as low and high float switches (electronic), absolute fail safe float valve (mechanical), RO/DI shut-off solenoid, and a reservoir to limit available water. Any and all of these parameters should be dealt with by an aquarium controller, not a set of tack on probes and simple monitors. It's like cable tying a Ph monitor to a light fixture and selling it as a water quality management device.
According to the authors numbers, 18% of the water gets partially filtered and supplemented per month. Alternatively, an 18% water change would remove 100% of the "bad stuff" and 100% restore 18% of the water to proper levels. What the unit does and does not remove is vague from what I have read. It doesn't appear to remove secondary metabolites for example. These are the toxic chemicals that stunt the growth of corals and in some cases cause necrosis and or mortality. Secondary metabolites are chemical agents that corals and algae release into surrounding water in order to compete for space on the reef, a process called allelopathy or "chemical warfare" as some people call it. In the open sea these allelopathic toxins are quickly diluted, only effecting neighbouring corals, but in a closed reef system these harmful chemicals can linger for quite some time. They can be removed through ozonation, UV irradiation, ion exchange resin, polymeric absorbent, protein skimming, activated carbon, and of course the good old fashioned water change.
Modern filtration methods have made water changes a lot less necessary than they were in the past. Now that phosphate binding media is fast, cheap and effective, we don't need to change water to remove phosphate. Well designed refugia further reduce phosphate and nitrate. Sand beds, denitrators and carbon dosing also contribute to the point where water changes are not implemented for nutrient export.
Before we look at how to change the water, we need to decide why we are doing it in the first place. What are we taking out and what are we putting back in? In some case it may not be necessary to do regular water changes, but if you are adding chemicals to buffer the various water parameters you are adding extra ions that don't find a "partner". A buildup of these extra ions (free radicals) causes ion antagonism as the left-over ions such as sodium and chloride wreak havoc with chemical interactions. Water changes provide a level playing field as the water is restored in an ionically balanced fashion.
The other reason for water changes is to remove the "unknowns". Personally, I don't think there are any unknowns. There are heavy metals that accumulate through nutrient import (feeding), and the secondary metabolites that I mentioned above. Other than that, the unknowns are completely... well unknown to me.
I honestly don't know much about what a Dailyseas unit removes, but it may remove some "good stuff". There are probiotics in the water that feed corals and consume excess nutrients (bacteria/microbes). The Dailyseas unit may directly remove these if they are large enough or indirectly remove them if they are attached to particles too large to pass through the membrane.
I don't think the opponents of the Dailyseas unit are focusing solely on the cost. Water changes are just far more efficient and simple. If water changes were truly challenging then such a device would have merit, but that simply isn't the case. There are many ways of implementing an automated water change system. Personally, I like to do it manually as automated systems don't vacuum the substrate or flush out detritus from rock work; getting in there and removing detritus as the primary goal and taking with it water as a secondary benefit. There is a lot more "bad stuff" (TOC/total organic carbon) in particulate matter (POC/particulate organic carbon) than there is dissolved in waste water (DOC/dissolved organic matter).
Stating that the Dailyseas unit replaces the salts it removes is an over simplification of the chemical process that goes on in our reef tanks. Every time one adds calcium in the form of calcium carbonate, calcium chloride, calcium hydroxide, or calcium gluconate, the buffer system is effected. In some imbalanced reef tanks it's a constant battle of adding carbonates (sodium carbonate & sodium bicarbonate) to raise the carbonate hardness (DKH) only to have it fall out of solution and precipitate (snow) or drive down the calcium level. The ionic balance of a reef tank can be put partially in check with water changes, but a Dailyseas unit only handles part of the "problem", at a greater cost, using more resources, and with fewer fail safes.
...but as the saying goes, I'd rather be lucky than skilled.
