I am pretty happy with the overflow; the things are expensive though!
So I gave the pukani a muriatic acid bath today and here is the process I went through:
1) I soaked the rock in tap water for 24 hours to soften organic goodies hiding in the rocks many crevices. (bonus points for soaking them with powerheads to let the water movement help shake things loose)
2) I got a container big enough to hold the rock as well as give some room around the sides for stirring (I used a tupperware container)
3) I read the instructions & safety warnings thoroughly before beginning then I put rock in the container and filled the container with water until the rock was covered with water and keept track of how much water I used so that I could mix the proper ratio. With this stuff I used 1.5 pints per 5 gallons (1 pint per 5 gallons was the "etching concrete" number and I wanted slightly stronger than that)
4) I added acid into water (avoided pouring directly onto rock) and gently stirred with a wooden dowel.
5) The rocks sat in the bath for about 30 to 45 minutes each before the bubbling died down to a minimal level.
6) The rocks were removed from the bath and sprayed off on all sides to remove the gunk.
7) The rocks were soaked in tap water for an hour to remove residues & the process could be repeated if further cleaning is needed (most people I have heard do this process twice or wish they did)
8) After acid baths are done and rocks are rinsed and have soaked in tap I have moved them into a bath of treated tap (RO would have been good) with powerheads to remove any residues and I will replace the water several times over the next 24 - 48 hours.
9) After this period I will take them out and let them dry out completely and remove any hangers on (sponges most likely)
Presoaking REALLY helps. I got all kinds of stuff out with just plain water (Urchin spikes and bodies, various crab parts & bodies, various gunk)
The acid really gets the protein and other contaminates out.
Even after being sprayed off after the first acid bath the gunk kept coming out.
Second rinsing and still getting junk out. These rocks are extremely porous which is what makes them so good but it also makes the cleaning process a little more difficult - but worth it in my opinion.