Help Ascorbic Acid and Potassium Sorbate -- Needed for both DIY Macros and Micros?

[Naturescapes_Rocco]

Hi all,

I'm finally making my own DIY ferts. I'll be trying the PPSPro regime and adjusting it as necessary for my 150cm rimless tank (looking forward to sharing my journal!).
Using GLA PPS-Pro (EDTA) Ferts (macros and micros mixed+dosed separately). I also already have some Ascorbic Acid and Potassium Sorbate powders, too. I will only be using RO water to prepare the fertilizer solutions.

From my understanding, Ascorbic Acid is used to keep the pH low enough for proper chelation of certain compounds in the Micro mix, and helps the Potassium Sorbate inhibit mold better at a lower pH. I plan on using 0.5g/500mL.

Question 1: Is Ascorbic Acid recommended/required for Macro mixes?
I found a few different resources saying no, and even some saying that it causes oxidation of some of the compounds over time, even changing the color of the mixture from clear to rust/orange if left alone for long enough.


Then, Potassium Sorbate -- an important Mold inhibitor for Micro mixes. I plan on using 0.2g/500mL micro premix, but:
Question 2: Is Potassium Sorbate required in Macro mixes?
I've seen resources state that macro salts shouldn't ever get moldy to begin with, but it can help keep the dosing tubes clean of any contaminants.

Still trying to figure out if I need to add the acid/preservatives to the macros at all (I will be using 0.5g AAcid+0.2gKSorbate per 500mL Micro solution).

Let me know, I'll be mixing my first batch tonight!

 

[Burr740]

Dont need ascorbic acid for the macros. They arent so volatile in solution. PH around neutral is perfectly fine. It does cause the solution to turn a little bit brown after a couple of weeks. To my knowledge that isnt a problem. But most people dont like it and it isnt needed in the first place. Do use potassium sorbate with macros to prevent mold, .2 grams per 500 ML

Use ascorbic acid with micros, .5 grams per 500 ML. Primarily its to set the PH. Micros dont tend to mold in the way macros do, the ascorbic acid provides all the prevention micros need via the low ph. Micros dont need the potassium sorbate, but it wont hurt anything either. I use both in my retail micros just to ensure an extremely long shelf life in solution (currently 8 years and counting..)

 

[Naturescapes_Rocco]

Exactly what I needed Burr, thank you!

 

[Naturescapes_Rocco]

Hey @Burr740, since you're quite knowledgeable on the subject:

I use RO water exclusively in my tanks and remineralize accordingly, but only just started DIY fert dosing. I currently use APT Sky from Dennis Wong's 2hr Aquarist, which adds both Ca and Mg in a ~ 4:1 ratio. I add 28g Sky to 55gal of RO water, which gives me about 8ppm+ Mg in the water column just from RO remineralization.

My question is: When remineralizing with a powder like APT Sky, which adds plenty of magnesium, do I even need to be adding the PPS Pro recommended Magnesium Sulfate to my DIY ferts?

I just realized that's a LOT of magnesium in the water, like around 10-12+ppm Mg, if I'm both remineralizing with Mg from APT Sky and from my DIY ferts.

Let me know when you have a chance, thanks so much for your time!

 

[Burr740]

10-12 Mg shouldnt hurt anything, but you definitely dont need the extra from pps-p if youre using Sky

Alternatively, since you apparently already have a dry form of Mg that youre using with your diy, you could use CaSO4 for your Ca and ditch the Sky altogether. Commonly called gypsum, can get 5 lbs for $18 shipped on amazon

1/4 Tsp adds 5 ppm to 10 gallons. Can do the math from there for whatever level you want. Anywhere from 5-10 should be good

My tap comes with around 35 ppm Ca, and 4-5 ppm Mg. Ive tried a lot of different levels of Mg along with that 35 Ca. Spent at least 2-3 years at both 10 ppm total, and 15 ppm total. I never saw anything bad but never noticed a benefit either. Probably 3 years ago I stopped adding any extra at all, just the 4-5 ppm in the tap along with 30-35 Ca. That works just as well as anything else Ive tried

One thing Ive learned is for whatever reason, we cant always go by crop study ratios for our aquariums. I could name a few, and the commonly cited Ca:Mg ratio of 3:1, 4:1 etc just isnt that critical for us. Some may have noticed a certain ratio works better, but I havent

*Not saying ratios in general dont matter because they do. Just not this particular one imhe

 

[Marwen]

You don't really need to use a preservative for micros for our application (non-commercial DIY ferts) because they already contain for example copper sulfate in high concentration which is already anti-bacterial/anti-fungal. In fact, copper sulfate solution has some applications as such outside of the hobby, copper being toxic in high enough concentrations after all. Zinc comes next in terms of toxicity, followed by manganese/boron.

For macros, you do have to use a preservative.

I would also still lower the pH to anything between 3 and 5 (using any weak acid like ascorbic acid, citric acid, acetic acid, etc.) if you really want it to last and not have to do this as frequently. This is for 2 reasons:

1) Potassium sorbate (an anti-mold/yeast agent, less so against bacteria) significantly loses its effectiveness above pH 6.5. It's most effective at pH 3 to around 5, then gradually less so the higher the pH. Same goes for other common food preservatives like sodium benzoate (which is more effective against bacteria than mold). This is why stuff like soda, yogurt, etc. that use combinations of these preservatives get slightly acidified.
2) Lowering the pH in itself helps to preserve the solution for longer (the lower, the more so).

 

[Naturescapes_Rocco]

Thank you both, these clarifications are really helpful!

 

[*Ci*]

Based on some info from GreggZ, I’ve been putting 10ml white vinegar and .4g of potassium sorbate per 1000ml of stock solution for both macros and micros. Does this sound about right? Maybe I don’t need to do the micros, but it doesn’t hurt?

 

[Marwen]

Based on some info from GreggZ, I’ve been putting 10ml white vinegar and .4g of potassium sorbate per 1000ml of stock solution for both macros and micros. Does this sound about right?

Yep.

Maybe I don’t need to do the micros, but it doesn’t hurt?

With micros the most important thing is dropping the pH to keep the chelate and the metals stable. Adding a preservative does not harm and helps your mix's shelf life. Potassium sorbate (known as E202) is super common food preservative (beverages, dairy products, etc.). Typical concentration in food is 0.02% to 0.3%. The concentration you're using (popular in the hobby) is 0.04% so on the lower side. Completely harmless to the tank's beneficial bacteria when dosed and diluted in the tank.

All commercial fertilizers use such preservatives, if not stronger (and kinda more controversial) ones like methylparaben. Along with mixing and packaging the fertilizers in a sterile environment which has a big impact on shelf life as well.

In any case, if something is wrong with macro/micro mixes, it'll be apparent (precipitation of solids, mold growth, etc.). So if you're not seeing any, you're all good.