I have been spending a bit of time pondering monitoring in aquaponics again. I think it has a lot to do with my aquatic ecology background – seasonal shifts in nutrient supply, nutrient sources and sinks, seasonal growth and die-backs. Before embarking on the aquaponic journey I was well on my way to do a PhD on ecosystem energetics but the funding never panned out and I abandoned that idea.
In aquaponics, things work a bit differently but it is not always all that easy to get your mind of details that you are used to expecting. DO, ORP, BOD, COD, TAN, TOC…….and the list goes on when you try to balance the ecosystem energetics of an open aquatic system. I see also on the automation group’s page that there are a lot of electronics junkies that seem to want to automate home systems to a great degree. I think there is it also a case of curiosity meets ability. As a further bit of detail, I will add that I have made this year my “Year of the plant”. I have always had a better handle on the fish and water component, are having fun with designing components and all, but feel that I will only be truly happy with my abilities if I get sharper at knowing exactly what plants want. This obviously lead to a bit of reading on the matter, and inevitably also looking at how these guys are treated in hydroponics. I know enough about the differences between the two methods not to try and emulate hydroponic conditions, but still, having come from a fish side, I was considering all things.
Working with my research unit put me into finer water quality monitoring mode with ammonia, DO, nitrates, ORP, EC and TDS on the radar. I am basically running fish and duckweed together with nothing else to deal with water quality except solids removal. To have publishable results, and to track how the duckweed deals with trace elements added to the system, I need to have greater detail that for typical applications.
All of this got me wondering though. Reading through terse exchanges on other forums reinforced the idea with me that there are two camps in monitoring theory: The minimalists and the detail freaks. I do not put people that are away from their systems often in any camp here – if you are not next to your system on a daily basis, or running a large commercial operation with a lot at stake, things are obviously different. But for the rest of us, for the typical home system, what is eventually the difference between monitoring essentials and excessive sampling of factors that is of no consequence? When a unit is hardly registering nutrients, what will parameters dealing with EC, TDS or ORP tell you?
If you keep the fish happy (give them food and have enough space and oxygen in the water), keep the bacteria happy (have a pH at which they can operate, enough oxygen and alkalinity to buffer the nitrification process) and keep the plants happy (nutrients, oxygen and a close pH match considering that bacteria comes first) will any of the parameters typical of finer aquaculture or hydroponic management matter? If you break this list of AP happy conditions down, you are referring to oxygen often, to pH often and then to basic nutrients linked to water quality. The obvious choice is to look at Ammonia, because that is the basis for the nitrogen cycle and the thing that will kill fish the quickest if you do something wrong.
What is nice about the list above is that it is typically stable parameters in a well managed system. pH is not 7.2 today and 6.1 tomorrow unless you have issues. Without hardware failures, your DO will closely reflect the stocking densities and gravel surface area you chose to work with – design and management issues – again not concepts prone to sudden shifts. Leaving dead stuff floating around or getting your feeding rates all wrong will show up in Ammonia readings, and it will show up quickly. Then again, if you know your system well, you would probably “see” the issue from the appearance of the water, the behaviour of the fish or even the smell of the unit. Are we insane to want to hook up a healthy ecosystem to life support?
Perhaps. In defense of detail, it is possible that well-monitored systems may reveal some aspect of system performance that we could otherwise overlook or not take seriously at present. Aquaponic practice is not totally developed and thus I think having a lot of detailed observations will be good. That said, I do not think it should be considered vital at all. As mentioned before, if you are away often or run a big commercial concern, the focus of monitoring is different, but for the rest of us, we perhaps need to accept the simplicity of what we are dealing with and settle into enjoying the stability we have created.