GDA Thoughts
First off my observations here are for my tank only and shouldn’t be take as absolute for every situation.
I have been observing some things in this tank over the last few months. Mainly since the powerhead mess. Firstly, the plants always perk up and pearl more one water change day and for a few days after. Normally I’d blame that on poor CO2. However I don’t have any of the other issues that go with poor CO2 and for just about two months I have been rocking my
@Yugang reactor so let’s throw that issue out.
What else happens on water change day or for a few days after? Front loading macros that’s what. The GDA has really only been showing up towards the end of the weekly water change cycle. IF I get in some extra water changes (more frequent macro dosing) it hasn’t show up.
My macro routine is front load 20-5-26 NPK based on changing 50% of the water. I use 32 gallons to determine my dose.
Based on this line of thinking I used rotalla buttery fly to some accumulation modeling. I could’ve used excel but rotalla butterfly is easy to use once you figure it out and you can’t break formulas with fat fingers.
Here is the boring base line graph using 20 ppm NO3 as a target. This assumes a couple thing. One that the plant uptake and water generation equal each other. So it’s a nice perfectly flat curve. Secondly RB assuming your dose amount is for the full tank volume so for my 50% water change I had to change my dose from 20 ppm to 10 ppm for it make sense. All things being equal front loading should be a flat line of accumulation.
View attachment 4514Now here is the same dosing regime assuming a 1 ppm daily uptake from plants for NO3
View attachment 4515
Notice how towards the end of the week the NO3 is getting lower and lower? My tank is very lightly stocked, maybe 20 small fish so there is virtually no bioload to generate much in the way of NO3. So I did the model again for 2 ppm daily NO3 uptake which is more realistic for my tank.
View attachment 4516As you can see it bottoms out pretty quickly. I wasn’t totally satisfied with that one so I shortened up the time period to more closely match the time frame for when I’m seeing the GDA show up.
View attachment 4517So if go more that two weeks without any extra water changes the NO3 starts dropping out which pretty much exactly matches the GDA issues I have been seeing.
I only used NO3 because it was first on my mind when I started down this rabbit hole, it could very well be PO4 or K bottoming instead.
Based on this I’m going to significantly up my front loading or maybe even switch to straight up EI style 3 x per week but I’m not sure which yet.
I am also musing the idea that the micro issues with certain plants that I’ve been having is directly related to the macros bottoming out. The micro symptoms have been sporadic (pallustrus white spots) very similar to the GDA coming and going and I think when the macros are good the sensitive plants are fine with XXX ppm of micro. Inversely when the macros start bottoming out or getting too low the micros start becoming an issue where the ar mini, chamelon sword etc. start throwing a fit.
I could be 100% wrong on all of this but this makes the most sense based on what I’m observed. It could just also be conformational bias and the real answer is I just stink at this.
Got back from being a jet flyin, wheel dealin, kiss stealin, son of a gun very early this morning. Tanks were without a water change for 8 days so once I got some rest I got to water changes. AR mini and chameleon sword look way better now and I hope it continues.
