Thoughts on this rip rap rubble rock

[chazman113]

So I was driving through south florida and on a whim I stopped by a landscaping supply company to see if they had anything I could use. I bought a couple pieces of this "rip rap" material that was pennies a pound. I was thinking of breaking it up and using it as fuge rubble for some extra surface area. I took introductory geology in college to dodge taking chemistry, so I'm a bit of an expert. I looks like just sedimentary limestone. Any thoughts? I broke some apart and can't see any discoloration that would indicate metal in it or anything.

 

[Timfish]

I'd use it. I use roughtly 50% local limestone in my tanks. Only down side I see is though looks fairly solid it also looks also rather soft so it may break apart easily in a system and may not be stable at the bottom of of aquascaping. I'd expect it to work great for your intended use in a sump/refugium

 

[Euphylliaphyle]

I used a rock wall of this stuff at a prior home that had more acidic water than many. It helped me get to the pH and hardness I needed to breed African Cichlids, and fwiw, it did not crumble under the weight of the pile despite the acidic source water, even thought it was obviously changing the water chemistry. Ymmv. I never used it for a reef tank in any capacity.

 

[chazman113]

I'd use it. I use roughtly 50% local limestone in my tanks. Only down side I see is though looks fairly solid it also looks also rather soft so it may break apart easily in a system and may not be stable at the bottom of of aquascaping. I'd expect it to work great for your intended use in a sump/refugium

Yea thats what I'm thinking, its pretty dense and brittle for a display tank but just for rubble and some extra surface area it seems fine. I'm putting some in slowly and see if there are any PH spikes, diatom blooms or anything of the sort. The dry rock prices are pretty expensive these days.

 

[Timfish]

I'd expect some kind of change in algae. Whenever I add more sand, disrupt the sand bed or move, adjust aquascaping for whatever reason I'll see increases in algae for awhile. It's expected and I won't do anything more than maybe just siphon some out when I do a water change.