<a href=showthread.php?s=&postid=7182285#post7182285 target=_blank>Originally posted</a> by GARFVolunteer
The rock may look good and be very strong, but it will be as useful as a cinder block for filtering...
[/B]
Very True - Over the last two months or so I've been experimenting with various rock recipes. I have yet to find any recipe that is good for any sort of "Live Rock". By that, I mean any rock with any respectable amount of porosity able to harbor life of various sizes.
I'd say I've done close to ten different batches now and in summary any rock that had a decent shape and visual appeal, (branches, shelfs, anything for that matter) - ends up being very dense and virtually non-porous.
I've had some batches that were more porous, but were to brittle to be able to stack or arrange in a tank. And I've had a lot of batches that simply never set up properly when modifying the recipe for porosity.
I've been using crushed coral as the "arago" part of the mix - and a bag of portland cement from HD.
I've tried various additives or substances to be used in place of some of the crushed coral - with little success. Various cooked and uncooked pasta - I havent had a recipe cure yet properly and hold.
My personal favorite and I still think most promising additive is nylon window screen material. I choose that becasue of the little squares, I figured they would be ideal for tiny air gaps. I cut it into about 4 inch wide strips and crumpled themand kind of dipped them in the aragocrete mix. Those set up properly, but were not very natural looking at all. I then tried 1/2 inch wide strips and I think my mix was too thin because it ended up stringing apart. Then I basically shredded the screen into 1/2 inch wide by 1 inch long bits and mixed those in (crumpled up as much as possible). I mixed that in with some of the basic aragocrete recipe and thats outside now - I'm not sure if it will cure. The mix looked good to me, but I might have had too much or too little cement - not sure why I'm having trouble with getting the cement to cure properly. I end up with a "mushy" rock.
Oh, I'm also doing this in a sandbox outside - and for the rock that I have mixed up right (and comes out overly dense) - you can make some good shapes - dig some holes and make some valleys and mountains in the sandbox. "Drip" the mix onto it, then you can add a huge mountain of sand and then drip some more over that and make all sorts of table structures and things with fold etc - but in my opinion way to dense to be useful.
I have gotten some surface porosity by throwing and/or rubbing rock salt at the shapes once youre done pouring them. I happen to use calcium chloride / sodium chloride salt, but I cant see anything wrong with the magnesium chloride either (any basic ice melt rock salt).
I'll keep you updated if I ever make anything useful.
