brightwell aquatics potassium- p

Yes, it's great stuff but when you start testing with the Salifert Potassium kit, you'll quickly find that K is nearly impossible to keep at 420ppm, especially if you have a lot of growth...and it gets really expensive. Especially expensive if you run an Algae Scrubber, they suck K down like a kid sucks down a milkshake.

I took the advice of Justin Credabel and went and got a 40lb bag of Potassium Chloride water softener salt for $25 from Home Depot. You mix this up thoroughly and then drip it through dry GFO to get rid of impurities. I haven't actually done this yet, but this is what Justin does so I trust what he says.

I emphasized thoroughly because dripping this stuff too soon after mixing can lead to disaster - for fish and corals. You have to mix it until the KCL is fully dissolved, then agitate it well for several hours to make really really sure it is fully dissolved.

I don't have a water/salt mix ratio figured out yet, but this is by far a cheaper alternative to Brightwell Potassion-P...which I would still recommend for anyone.

The only beef I have with them is that they still haven't updated their label more than 2 years after I pointed out an error on it that causes you to mix the stuff to 3x strength if you don't pay attention.

http://www.brightwellaquatics.com/products/potassionpt.php

They say 2 tsp is 5g. This is INCORRECT. Each level dry tsp is actually 7.5g, so 2 tsp is 15g. This error results in a solution that is 3x what they say it is, and if you don't let this stuff completely dissolve, you guessed it, dead stuff. I'm actually really surprised that no one has complained to Brightwell about this error killing things. The way I found out about it is because another user on another site was adding the powder directly to his filter sock and blammo, dead stuff. So he stopped doing that and mixed up a solution and dosed it shortly afterwards and blammo, dead stuff.

Moral of the story: test, dose 1/4 of what you think you need, wait 30-60 minutes (depends on water volume, for mixing) test again. Dose 1/2 of what you think, test again after a while. Make sure you are not overdosing, and make sure the solution is thoroughly mixed (and there is no undissolved powder left - if there is, your solution is saturated)