Backyard Aquaponics
A place to discuss aquaponics

anyone know if it makes a difference if you supplement your pond water with maganese sulfate or magnesium suflate (epsom salt)?

The local supplier sells maganese sulfate for $55/50 lbs and magnesium sulfate for $13/55lbs. I heard maganese sulfate is better but magnesium is like way cheaper. Plus I bought it already. Is it OK to use?

Thanks

Interesting question.
I can't find anything on the internet.

That's funny Trevor, I looked too! It said you can use either but some sites said they are not the same but didn't explain. Chemists out there?

Why do you feel the need to use either???

Won't a sulphate make the water more acidic?

Yep...

The University of Hawaii uses maganese sulfate for a magnesium supplement. They found that magnesium was lacking in the system they developed. They add very little, like 1 gram every several weeks. I was wondering if magnesium sulfate can accomplish the same thing.

Oh and I guess related to this topic, I found potassium bicarb cheap! Finally found the stuff. I got it at 5 bucks a pound. Not that cheap when I had to pay another 5 bucks to ship it though. Living in Hawaii is lame sometimes.

If they were trying to supplement Magnesium... then they would have been using Magnesium Sulphate (Epsom salts).....

Using a Maganese compound wont supplement the system with "Magnesium"... just with Maganese....

Usually, in aquaculture, it's used for "hardness" rather than plant supplementation...

In general Magnesium deficiencies are somewhat rare.... and if it was the case, then the plants are more likely eficient in other trace elements as well...

Unless their pH was within certain ranges... it would have been a waste of time anyway... as any uptake would be locked out... along with other elements... (see above)

Ok I was incorrect in my statement. Rupe, you are right, they are supplementing MAGANESE not MAGNESIUM. So the I feel very stupid because now I realize they are 2 different things.

Maganese sulfate for maganese supplement (needed)
Magensium sulfate for magnesium supplement (not really needed)

Crap.

So now I have 50 lbs of magnesium sulfate and I have no idea what to do with it....

You may find that your Epsom Salts are of more use in an AP system than a "Maganese" supplement..

Just had a cursory glance at the "manual" they have produced... frankly I'm completely un-impressed...

They seem to have heard that aquaponics is a combination of "aquaculture and hydroponics"... and literally proceeded on that basis...

And create a chemical soup as though they were growing hydroponically... and use Magnesium Sulphate as one of the base chemicals in the hydroponic soup...

You would be better off reading through the forum basics and duplicated a traditional AP setup... or, if you're really set on a raft system ... ala UVI.... take a trip out to "Friendly Aquaponics" and see how they have employed the UVI style model...

After reading the manual... I think that, other than perhaps the fact that they are using Tilapia.... they will eventually kill ALL their fish...

Have little idea what they're doing... and have missed the point of "aquaponics" completely...

I also jsut don't believe their figures... and believe that they would get exactly the same result just using hydroponics...

Although with their own chemical "nutrient" mix... they would in fact probably not acheive their results... if it weren't in fact due to the other elements/nutrients being provided by the "aquaponics" component...


IMO... this is a "sloppy" piece of applied science... that has yielded results... but not based on the inital premises... more by good luck...

Hi Rupe, thanks for the feedback regarding the manual. Can you be more specific on your comments?
What would kill the fish? Lack of bio filtration? Too much chemicals?

You see, I felt the same way as you did but it works and works well. After he presented his research I didn't feel it was dumb luck. The dude did his research. But I still can't get my head around a lot of the stuff like you said.

Actually the system was modeled after hydroponics. It was studied to why hydro worked so well and then fish were integrated into the system.

Is magnesium supplements needed? I am not interested in lowering my pH so the only reason I'd use it is for magnesium supplements.

Thanks!

As Rupe Said, the Magnesium sulfate is often used to adjust water hardness if that is needed in the system.

However, if you are not seeing a hardness issue in your water and you are not seeing Magnesium deficiency in your plants......

You can always use the Magnesium sulfate to take a muscle soothing bath after a hard day of washing gravel. Epsom salts need not go to waste though a 50 lb bag might last a little while and take up some space in the bathroom.

I've still got 350kgs of Epsom salts from my float tank. Nice to know I can lower the PH.

I don't know that I would go using too much magnesium sulfate in an effort to lower system pH. You might wind up with way too much Magnesium.

I believe you want to keep a balance between the magnesium and calcium but I'm not sure exactly what that balance is or how to test for it.