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Using DMSO To Dissolve Difficult Aquarium Medications


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Using DMSO To Dissolve Difficult Aquarium Medications

With a recent outbreak of columnaris, I found myself using medications I had been previously fortunate enough not to need! In doing so, I used an organic solvent, DMSO or Dimethyl Sulfoxide to “pre-liquify” if you will, relatively insoluble (in water) medications like praziquantel and nitrofurazone. In my case, I used nitrofurazone and kanamycin powder as opposed to prepared remedies that employ them such as API Furan-2 and Seachem’s Kanaplex although I have dissolved Furan-2 with DSMO in the past.

I like to dissolve fish medications in DMSO before administering it as it makes the solution linear and without any particulates. Highly insoluble medications like praziquantel and nitrofurazone ‘vanish’ into a clear, thick fluid if placed in DMSO upon which it’s adding to the tank.

I had a recent batch of fishes for QT and grow-out develop severe columnaris. My guess being it was the 2nd strain as it killed all fish with lesions in 24-48 hours after they first appeared. They began dying with no visible symptoms at a rate of about 1/day until one developed what appeared to me, to be a classic columnaris ‘patch’.

I began a nitrofurazone/kanamycin treatment immediately and fortunately it stopped the deaths just 2 days into medicating. Eventually all the lesions cleared up and they are growing out well.

I used nitrofurazone in DMSO as it becomes a clear, liquid ’syrup’ if you will with no particulate at all present. It apparently finds itself in use with praziquantel as well:

DMSO Dissolving Praziquantel

I used this DMSO: NO ODOR DMSO - Dimethyl sulfoxide liquid (3.4 Oz - 100ml), Pharmaceutical grade, High purity, by Heiltropfen:


However, I was originally concerned about the efficacy. That is, if using DMSO to dissolve medications, which results in essentially no particulate, but dissolved in normal water shows particulate, would the dosage be different in the DMSO dissolved medications as more of it is in solution?

In addition; DMSO easily absorbs into skin and according to the findings below, the fish absorb it as well. So then would we need be concerned that medicated fish with DMSO-dissolved medications may see still more medication than had it been administered in water?

My recent experiences would suggest otherwise-though this is far from scientific! I used the recommended dosages but used DMSO to dissolve the nitrofurazone and all went well. I witnessed no fatigue in the fish and the infection cleared up. This of course only tells me that I did not reach any toxic levels BUT, did I effectively increase the dosages by using DMSO or did DMSO simply make it go into solution better?

The following however is much more scientific.

This excerpt from the document below would suggest DMSO does not alter the dosage and only improves solubility in water for many medications that are difficult to dissolve in water. It’s an old study (1966) of using an antibiotic dissolved with DMSO vs. simply in water, and testing the fish for various levels and it found almost no difference between the DMSO medicated fish and the default. This would suggest the DMSO’s value is almost exclusively for medication solvency.

It has been my experience that I’ve never seen a negative effect from using DMSO to dissolve aquarium medications and it unquestionably makes medicating the tank MUCH easier when the medications are difficult to dissolve in water.

I do wish this could be more comprehensive and less anecdotal but it’s most definitely worth trying if you find yourself in the unfortunate situation of needing to utilize the likes of nitrofurazone, praziquantel or other medications that exhibit difficult solubility in water.

This old study from 1966 suggests it will not affect the dosage by improved solvation nor by direct absorption by the fishes:

Bureau of Sport Fisheries and Wildlife
Fish Control Laboratory, WI.


A preliminary test was performed to determine what, if any, influence DMSO has on the toxicity of antimycin to bluegill. Various concentrations of antimycin were added in combination with enough DMSO to produce 1.0 p.p.t. of DMSO in the test vessel. A comparison test was run using only acetone as solvent for the antimycin.

The 96-hour LC so of antimycin and acetone alone was 0.089 parts per billion (p.p.b.), while antimycin in combination with 1.0 p.p.t. of DMSO produced a 96-hour LC 50 of 0.084 p.p.b. These results reflect biological variation and indicate that DMSO has no effect on the toxicity of antimycin at 96 hours. It is possible that in a bioassay designed to yield toxicity with shorter exposures, DMSO could enhance the absorption of antimycin sufficiently to affect toxicity.

Ball (1966) compared the relative toxicity of 0.05 p.p.m. p,p’-DDT to goldfish when used in combination—with 6 and 18 p.p.t. of either DMSO or acetone. His results indicated that
DMSO does not significantly affect the median survival time of goldfish when compared to acetone. He further suggested that DMSO may be a better solvent than acetone for pesticide
toxicity studies.

Rabinowitz and Myerson (1966) were unable to show a significant difference in the uptake by aquarium fish of radioactive labeled dyes when used in combination with 1.0 p.p.t. of DMSO.

1. The acute toxicity of DMSO to fish is of a very low order.
2. When the level of acute toxicity is reached, DMSO is abruptly and non-selectively toxic to the nine species tested.
3. Various water qualities at 120 C. have little effect upon the toxicity of DMSO to rainbow trout.
4. Increases in temperature cause a definite increase in the toxicity of DMSO to rainbow trout.
5. Preliminary results indicate that 1.0 p.p.t. of DMSO has no effect on the toxicity of antimycin to bluegill at 96 hours.

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Some medications never fully dissolve but they seem to dissolve well enough to function so I'm uncertain how much actual value my post has!

Certainly nitrofurazone and praziquantel always leave a good amount of particles and residue. Even with very hot water, they leave enough undissolved residue to question the actual dosage.

With DMSO, they become completely soluble. I've since read this method assures greater dosage accuracy in that virtually 100% of the medication is in solution. What the actual value of that is in practice, I really don't know. 

If nothing else, the DMSO makes it substantially easier to mix into the tank water.

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Guppysnail, I'm so glad you've raised that point about Prazipro as that very product is integral to the embryonics of this discussion and I had completely forgotten about it!  There seems to be some consensus as to the potential toxicity of the solvent used in Prazipro on very delicate species, at least in marine tanks.

In any event, this particular discussion locally began due to an incident at an LFS near me over the use of Prazipro in marine aquariums. Apparently the solvent used in Prazipro, Oxybispropanol, exhibits some 400%-600% higher toxicity than DMSO which would normally still be considered quite safe as it's still very low but in this case, it killed off all of his feather dusters. 

According to Humble Fish, it is the toxicity of the Oxybispropanol as opposed to the praziquantel as they had sited multiple 3rd party anecdotes but had similar results with tubeworm die-off but suffered no die offs when using DMSO. Oxybispropanol has also been known to damage the cycle in marine aquariums filters causing small ammonia spikes.  

I don't know if the detriments of Prazipro's solvent Oxybispropanol, is as much of a detriment in freshwater. But at least amongst reefers, it seems to be toxic enough to avoid use when invertebrates are present per Humble Fish:  

"Prazipro is generally considered reef safe, although it may kill any tube worms/feathers dusters you have. It may also eradicate bristle worms. This is important because the Oxybispropanol (solubilizing agent) Prazipro contains will sometimes cause a bacterial bloom (cloudy water) when mixed with other meds. If using a protein skimmer post-treatment, be advised that it will “over skim” for at least a week or so."

I had 5 marine tanks in the 1970s before canisters, protein skimmers and sumps - It was all sub gravel and carbon in those days and few ever heard of the nitrogen cycle.

To paraphrase The Producers

"I used the wrong filtration, the wrong equipment and had wrong information of the nitrogen cycle for years....where did I go right?!"

It's hard to believe our tanks ever survived back then!

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This is great information thank you for sharing. I love learning.  

On 10/8/2021 at 11:56 AM, dasaltemelosguy said:

I had 5 marine tanks in the 1970s before canisters, protein skimmers and sumps - It was all sub gravel and carbon in those days and few ever heard of the nitrogen cycle.

1970s was my freshwater start. Reading all the internet stuff these day I wonder how my fish survived so long 😳

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