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Discussion Starter #1 (Edited)
I’m setting up an auto-doser, so I’m planning on mixing my dry ferts with distilled water and having it under my tank. I’m worried about mold in the micros, so I’ll add some Metricide 14 to help with that. How much Metricide should I add to make sure there is no algae / mold in the dosing containers?

Edit:
I’ve been rethinking this, and is there anything wrong with just mixing my liquid ferts with the correct ratio of Glut already added? Here’s my math, so folks can double check me…

- My 125G tank is going to have roughly 80G of water in it after hardscape
- Using NiloCG DiY liquid ferts, the recommendation is 5mL / 20G of water, or 20mL
- NiloCG DiY liquid ferts is 1 packet of ferts / 500mL of RODI water
- I’m planning on doubling the amount of RODI water, and doubling the dose. This should help make the dose more consistent by increasing the total amount of solution dosed every day. Daily dose of 50% ferts would be 40mL / day
- The correct dose for Metricide 14 is roughly .75mL / 10G, or 6mL / 80G.
- If the total dose is 40mL daily, then the liquid mix for 1000mL of solution should be 150mL of Metricide 14 and 850mL of DI water

Does all this math make sense to everyone else? Will 15% Metricide be enough to prevent mold and algae in my dosing containers and tubing? Is there any chemistry reason not to add this much Metricide to the Macro and Micro mixes (precipitation, etc…)?
 

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Metricide 14 is 2.6% Glutaraldehyde. Excel is 1.5% Glut
Excel/Matricide = 1.5/2.6 = 0.58

By ratio, the equivalent dosage is as follows:

Initial after WC(2ppm): Excel 5ml/10gal = Metricide 2.9ml/10gal
Daily afterward(0.4ppm): Excel 5ml/50gal = Metricide 2.9ml/50gal
 

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Some members do you use glut as a preservative. I use food preservatives as an alternate, as do many others. My concerns with the glut (Metricide or Excel) is that it may destabilize over time. It is certainly sensitive to light and will lose it's killing power when exposed to light. It also may react with any organics (if they appear) in the solution. If using it, I would suggest keeping pH below 5 and this is where the vinegar recommendation, above, can help. There isn't much evidence, either way, for my concerns, so you may be fine using it.

If you're interested in the alternative approach, use ascorbic acid (antioxidant): 1 mg / 1 ml, and potassium sorbate (mold inhibitor): 2 mg / 5 ml.
 

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Discussion Starter #5
If you're interested in the alternative approach, use ascorbic acid (antioxidant): 1 mg / 1 ml, and potassium sorbate (mold inhibitor): 2 mg / 5 ml.
Hi @Deanna,

As expected, I’m starting to have mold issues in my Micro mix, even after adding Metricide. With this alternate option, I feel like I would be adding a ton of chems. I’m mixing 1000ml at a time, would I really be adding 1g of Ascorbic Acid and 250mg of Potassium Sorbate? That feels like a huge volume to me, but perhaps I’m just not visualizing it properly.

Lastly, will either of these preservatives be influencing the actual micro dosing? The only nutrient I can see here is the K, but it looks like it is in a very small volume. I just don’t want to end up throwing everything else out of whack by adding more chems to my tank.
 

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I use 60 ml 1.5% solution of glut and 940 ml of water to dissolve my fertilizers. I use the PPS pro method.
 

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Discussion Starter #7
I use 60 ml 1.5% solution of glut and 940 ml of water to dissolve my fertilizers. I use the PPS pro method.
This is basically what I did, but I grew mold anyway. I'm going to change it up to Ascorbic Acid and Potassium Sorbate. It just seems like 1g of Ascorbic Acid and .25g of Potassium Sorbate is an awful lot of chems.
 

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This is basically what I did, but I grew mold anyway. I'm going to change it up to Ascorbic Acid and Potassium Sorbate. It just seems like 1g of Ascorbic Acid and .25g of Potassium Sorbate is an awful lot of chems.
I haven't looked at the articles behind this, but a final 0.1% w/v of ascorbic acid and 0.025% w/v of potassium sorbate (in 1 litre) doesn't seem too unreasonable to me.
 

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Hi @Deanna,

As expected, I’m starting to have mold issues in my Micro mix, even after adding Metricide. With this alternate option, I feel like I would be adding a ton of chems. I’m mixing 1000ml at a time, would I really be adding 1g of Ascorbic Acid and 250mg of Potassium Sorbate? That feels like a huge volume to me, but perhaps I’m just not visualizing it properly.

Lastly, will either of these preservatives be influencing the actual micro dosing? The only nutrient I can see here is the K, but it looks like it is in a very small volume. I just don’t want to end up throwing everything else out of whack by adding more chems to my tank.
Yes, those are amounts that have been known to work. I mix up a trace concentration of 3600 ml and add 3.6g Ascorbic Acid and 1.44g of Potassium Sorbate to it. I use it up over about a year and have yet to have mold issues. The ascorbic acid acts as an antioxidant and mild chelator.
 
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