Thanks for your feedback brother. Gypsum is brand new for me.
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The summary first: Iām, as I stated as plainly as possible, no expert in hydroponics or chemistry. Iām trying to learn. And it appears I was wrong with my concern for other desired cations in a hydroponic environment. I donāt think @ColeLennon has a problem after doing quite a bit of due diligence. I have no intentions to derail threads, and was only vocalizing my concern complete with warnings of my lack of knowlege or certainty.
Gypsum, on its own has a saturation limit of ~15mM into water. That equates to around 10g/gal, and implies only 2/3 of your 1 tablespoon (~30g/tbsp assuming high packing efficiency [which doesnāt appear to be the case, one of my first erroneous assumptions] - gypsum has a density of 2.3g/cc) is potentially into solution.
Things with your re-run figures (those amounts mixed into 2 gallons of water rather than 1 gallon) are less alarming in general. This combined with the fact that I went and MEASURED the mass of Diamond-K tablespoon to be 11g.
@shag I totally agree that Ca, even a LOT of it, doesnāt seem to be detrimental. My concern was primarily the surplus SO4 (2-) readily reacting with the other available cations such as K, which seems to be an unsupported hypothesis, both by your observation and Aqion software.
@ColeLennon I brought this up because I was concerned, but Iām not really worried about it anymore. Gypsum doesnāt seem to impact things in the same way as in soil (which is all I had learned about). I retain that you seem to be adding too much of it - most hydro sources I could find (Iāve spent several hours researching this by now out of sheer curiosity) seem to limit Ca application on the high side to about 200ppm. You can find that in LD50s thread characterizing miscellaneous nutrient regiments with plots of nutrients vs plant life cycle. Hereās @HolyAngel with his gypsum application rate which is
about 2g/gallon (~118ppm of additional Ca, my calculator and LD50s agree) Fertilizer Comparisons, Retail Mixes and Program Insights - #36 by HolyAngel
I measure 1 tbsp of Diamond-K to be 11g. So you are in excess of that recipe by about a factor of 3. If you replace the tbsp with a tsp youāll be right on that level.
This is a simple summary, this guy is really fantastic with lots of stuff related to plant chemistry subjects. Calcium Sulfate in Hydroponics
I think you are fine. Leave it! Ignore my earlier worries. They were based on my flawed assumptions that 1tbsp of gypsum would be ~30g (itās actually 10-12g), AND that the behavior of the gypsum in solution could precipitate other cations such as K
If you (or anyone else) want to play with the calculator values, youāre already pretty much setup here with the stuff you have been using, you can just change individual quantities and see how your concentrations move. Change the .pdf extension to .xlsx after you download. If youāve got questions about using it just hit me in a PM
Hydro Calculator FE Simple 9jul23.pdf (18.9 KB)
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That is killer brother and those #'s are way better. That is a lot of work. Iām grateful I have the ability to read the plant. Thank you for sharing this with me and everyone else. You are a valuable member of OG. Super Props. 
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Iām following this, always trying to improve my outdoor grows. Thanks guys.
So what is the best source of calcium - botanicare calmag?
What are you guys using
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I was using Foxfarm Bushdoctor Cal Mag for years. I switched to diamond k gypsum just over a month ago. Best grower move Iāve made this year.
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Ok, Iāll have a look around for those.
Pretty sure I can get the bush doctor anywhere.
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I bought 1 lb to try it. I will buy 5 lbs next.
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I went all thug life and just bought the 50 lb bagā¦ 2 years ago. Lol. I heap the gypsum into the res until itās no longer soluble. I canāt get rid of this bag. The one regret I have is that I didnāt break that big ass bag down into smaller batches stored in some kind of air tight container. Humidity from the room constantly infiltrates the bag. The gypsum stays ādryā but you can tell that there is added water weight throwing off the weight on dry measurements.
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fuckin gangsta
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Haha for real though it was like $19. Shipping was a mother fucker though. No one ever tells you that itās gonna be like $75 to ship a 50 lb sack across the country. Theyāre trippin. Chewy delivered my dog food for free aaannnd the bag was cheaper than Petco.
Shipping is a scam.
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Get a prime account and its free shipping.
Keep batches in these. I use 8 oz ones. Screw top. All my dry nutes are in these. If it clumps I donāt waste the whole bag.
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Nice. I had to double check another online store.
$11 for the 50 lb bag and $57 to fed ex.
Couple dollars cheaper to go with the evil empire.
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Dome topped the DJ Short this morning.
Flat topped half of each of the Wonder Dawgs. I will do the other half this evening.
Havenāt decided what I want to do with the Purple Queens yet.
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I havenāt even been able to use my HLG Blackbird yet. I want another LED. I will need one eventually since I want to have room for a 3x3 and 4x4. I do have enough restraint to wait for a price drop. 
Review on the HLG Tomahawk 650 bar LED
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one cool day in july and everyone wants to tend to their veggie gardens again 
fresh herd ready for slaughter in a week or two, inside with the ac on again.
you could probably automate the first water with just h2o though with a circle loop on a soaker connected to 1/2" line + cheap timer?
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Yesterday morning before I topped the Wonder Dawgs and Dome Topped the DJ Short Blueberry.
Pics this morning of the last topping of Wonder Dawgs and Dome Topping for the DJ. I am leaving the Purple Queens alone with perfect structure. The same goes for @Bobgrows 90ās Kush I called it right with only one FIM job on her.
Yesterday morning before beginning my toppings each pot got shots of Alaskan Fish Ferts and Big Bloom followed by an evening Kelp Foliar.
Thatās it on Toppings.
Thanks for following.
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Ok Alaskan fish fert do you pH your water after adding or because itās organic the soil sorts it out? I ask because I used it fine with no pH adjustment then 1/2 through the bottle it started screwing with my plants even though I used on plants that had finished no problem.
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The Gauntlet this morning. Been supplementing with Bushdoctor Sledgehammer last two feedings. July 21st I start supplementing with Open Sesame 5-45-19 for 2 weeks.
Thanks for following.
@420noob I donāt PH anything. I have never had an issue with Alaskan Fish Ferts.
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Damn @ColeLennon your plants are going dumb brother. They look great man. Joe is playing with my likes right now so Iāll have to circle back in a few hours!
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