Dissolving K2SO4

[ginaalan]

Hi Juggler,

I have bought the Potassium Sulphate (in powder form). Using Chuck's calculator, I throw in approx. 4 Tablespoons (4 x 15ml = 60ml) of powder into a 200ml of water. To my surprise, the powder does not dissolve readily in the solution, layer of powder was seen settled down at the bottom of the beaker even after prolong stiring.
Could you help to advise if the problem was due to insufficient water being used to dissolve the powder or should I be boiling the solution (or use hot/warm water) to get the powder to dissolve ? Pls help, thanks.

[Simon]

try to dissolve it before u pour it in

[Plantbrain]

K2SO4 is the least soluble stuff.
You'll have trouble making a solution of this.
Most folks that sell liquid K+, it's from KCl, not K2SO4.

Best added dry anyway.
Same for KNO3

Regards,
Tom Barr

[illumbomb]

Hi,

From my experience, you can dissolve max about 1 teaspoon of K2SO4 with 250ml of water at room temperature.

Regards,
Wang

[ginaalan]

Thanks guys for all the input.

From what I have gather, this is what should be done.
Dissolve 1 teaspoon of Potassium Sulphate to 200ml of water - probably can dissolve. The calculator gives a 0.04 ppm Potassium per 1 ml of solution for a 300 litres tank. Thus, by adding the entire 200ml(+ dissolved powder) of solution, the tank should gets (0.04 x 200) 8 ppm of Potassium.

Any comments on my above interpretation ?
Else this could serve as a guide for aquarist who like to try adding fertilizer in powder form.

[ckll]

If you are going to dump the whole 200ml of solution into the tank at one shot, then dont have to make stock.

Just add the amount you want into the bucket of fresh water during your weekly water change (assuming you use a bucket and it's a weekly change )

[FC]

I never throw powder into my tank, I find it a bit risky (of overdosing), especially for small tanks. This is what I have been practicing:
1) Use empty 250ml bottle
2) Add 20ml (approx. 50g) of K2SO4 power and dilute it by filling with water till full. Shake the bottle each time you use them.

For KNO3, I use also 20 ml of powder, KH2PO4, I use 2 ml of powder.

[vinz]

For K2SO4, I usually find it better to mix of the spot.

Use the "Add compound directly to tank" option and calculate the amount to dose to reach your target ppm. Then mix the dose with some water and dose the whole solution to the tank.

[juggler]

I used to prepare stock solution for K2SO4. Usually about 4 doses per bottle because the compound is hard to dissolve. But I found that some scum seem to grow in the bottle over the weeks.

I now dose the powder straight into the tank after water change. It will dissolve in a few hours.

[pat]

Just to share some info for dissolving K2SO4 into water when you do mixing using 12gm to 100ml of water.

[geoffrey]

Don't even think that boiling helps dissolve more K2SO4 and quicker because once your stock cools, they will crystalise again.