DIY Fish & Corals supplement using propylene glycol as solvent

[thejacgues]

Hi there,

I know that in general using propylene glycol as carbon source for bacteria in reef aquarium is safe and works great in reducing PO4. I dose it roughly 1ml / 100l in high nutrients system.
I wanted to create my own DIY supplement for both fish and corals (so I would add it to the frozen fish food, too).
Why? I'd like to add more omega-3 fatty acids, astaxanthin & fat-soluble vitamins to my stock via this DIY additive. Maybe in future, I'd consider enhancing it with amino acids and B-complex vitamins, if I only find some additives-free product to use as an ingredient in my formula.

My questions are the following:
1. Would propylene glycol act as a good solvent and preservative agent for a such mixture?
2. Could it harm fish if it's added directly to their food? I know it's used commonly is small quantities in human's food, dogs & cats food etc. I just wonder if the amount needed to solve all the ingredients would not be too high to use it directly on their food rather than adding it only to the water column.
3. Can fish efficiently & easily absorb amino acids, vitamins etc. directly from water?

 

[Randy Holmes-Farley]

I've not seen any reefers report using propylene glycol, but it may be fine. I do not know about high doses directly to fish.

It will do a good job of dissolving many uncharged organics.

I do not know if fish take appreciably dissolved small molecules, such as amino acids, directly from the water. I would guess very little, since only a relatively small amount of water will pass through their GI tract. Like a human drinking a beverage with only a few ppm of amino acids.

 

[thejacgues]

Thanks @Randy Holmes-Farley . I have been using glycol for over a year and I need to admit, it's probably the best carbon source of getting rid of PO4 that I have had so far. All classic DIY methods basing on vinegar or vodka seemed to target mainly NO3. Vinegar additionally lowered pH, and sugar resulted in many issues with unwanted organisms like bacterial infections.

What do you mean by uncharged organics? What else in reef tank, apart of PO4 and NO3 can be considered as such?

Solvent wise so far it seems to work well for fish oil, as I do not see any oil film on the water's surface.

 

[Randy Holmes-Farley]

Thanks @Randy Holmes-Farley . I have been using glycol for over a year and I need to admit, it's probably the best carbon source of getting rid of PO4 that I have had so far. All classic DIY methods basing on vinegar or vodka seemed to target mainly NO3. Vinegar additionally lowered pH, and sugar resulted in many issues with unwanted organisms like bacterial infections.

What do you mean by uncharged organics? What else in reef tank, apart of PO4 and NO3 can be considered as such?

Solvent wise so far it seems to work well for fish oil, as I do not see any oil film on the water's surface.

Organics always contain carbon, so nitrate and phosphate do not count. I mean things like amino acids.

To be honest, I'm not sure how a particular organic carbon source (like the propylene glycol) can have a substantially different P vs N effect compared to other organics. Perhaps denitrifying bacteria do not use it particularly readily, but remember that 1 mL of propylene glycol will have more available energy for biological processes than 20 ml of vinegar, so one needs to compare a small amount of propylene glycol to a much larger amount of vinegar to make the claim that it is the chemical that matters rather than just the concentration.