# Advice on Crumbly Lava Rock



## FlyHigh (Nov 15, 2009)

I'm starting a 100 gal tank and would like to use lava rock for caves and aquascaping. To minimize the cost, like some people, I went to my local nursery/landscaping dealer to purchase lava rock rather then pay a lot for the small pieces at the local pet store. I bought 2 large lava rocks, each was about 3 ft long and 1 ft across for $12 a piece. I kept breaking them on the ground until I got the sizes I wanted and I'm very pleased with the shapes and appearance of the rock. After a lot of rinsing, cleaning and soaking I am ready to place them in the tank. However, when I pick the rocks up from the buckets they've been soaking in, there is still a noticeable amount of rock that crumbles away if I rub my finger across the lava rock. If I were to dunk the pieces into clean water and then place them into the tank without rubbing them too much I doubt I'd have a problem but if I had to move them around a lot I'm worried about pieces flaking off or part of the rock crumbling away. On top of my obvious worry about the safety of my fish, I have a crushed coral substrate and do not want the substrate to become tainted from the rocks debris. I think that once the rocks are in place they'd be ok but was looking for some advice. Thanks.


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## DJRansome (Oct 29, 2005)

Power washer?


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## FlyHigh (Nov 15, 2009)

yeah, I might try that but it seems like as the looser parts break off from cleaning, that in turn creates other loose sections. When I say loose, I'm talking about a fine, grain of salt size debris that dislodges if I rub my fingers against the rock. Left in clean water over night, the water remains crystal clear and if I rub the rocks while submerged whatever rubs off does not discolor the water.


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## davegius (Nov 27, 2007)

I use lava rock in some of my tanks for the same reason that you have, and I have had a similar problem. I try to just lightly rub over the rock with my fingers to pick off fairly loose pieces and then put it in. You are still going to get some pieces coming off here and there once it is in the aquarium, and generally when I move a rock that has not been moved for a while and clean the substrate around it there will be a lot of red dust that has come off the rock and settled. I have been using lava rocks for 2 or 3 years now and have never noticed it to have any negative affect on the fish - other than the fact that it is jagged and fish trying to escape can noticeably scrape themselves up some times.


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## FlyHigh (Nov 15, 2009)

Thanks for the reply. I just got back from my LFS and realized that the lava rocks they sell there have the exact same properties as the ones I have. I'm a lot less nervous now about putting it in the water especially after your reply as well. I'll just be careful when placing it and if I notice my fish are hurting themselves I'll change it for something else down the road.


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## FlyHigh (Nov 15, 2009)

Update: The lava rock has been in my tank for over a month now. My water is as clear as can be. The lava rock has not flaked or crumbled at all once it was placed in the tank. I have not noticed any scratches on the fish either. I think I figured out why it was so crumbly and brittle initially. I purchased the lava rock as huge chunks. The outside of the rock, is normally more worn and slightly smoother. When I broke the rock into smaller chunks, the inside of the rock was more jagged and crumbly. I did the best I could in removing the loose material and rinsed it as much as possible. In the end, I am extremely happy with the way it turned out. Especially paying cents per pound instead of dollars per pound.

Also, I was able to drill into the larger pieces in different places with a masonary bit to create tunnels and caves. It was amazing how while I was drilling the hole, it looked circular and unnatural but after the lava rock was rinsed and the loose bits fell away, I was left with some striking pieces that look amazing. I may do some more drilling to create even more caves. I'll try to post pictures.


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