My rock floats!?

[kampkomfort]

I've been looking for some base rock in my area, and I've had a tough time. I finally found some ~40# rocks at a local landscaping firm that were referred to as "lava rock". They look very porous, and they are fairly easy to carve. However, they FLOAT in saltwater! I currently have a 20# piece in a saltwater holding tank, and it still as a small portion sticking above the water after several days. The pH hasn't changed at all (the rock is the only thing in the holding tank).

Is this really lava rock if it floats? How can I encourage its journey to the bottom? I'm in no hurry, but I would like to carve this rock into some custom shapes for my main tank.

Thanks for your help.

(I tried to post a small pic of the rock...it may not work out, though.)

[CoralKreations]

doesnt look very porous or like lava rock from the pic - but...

I dont know try turning it to remove any air...sorry but not much help there -


....do be careful with alternative rock though

[kampkomfort]

That image is somewhat deceiving. The rock's surface is fairly porous, and the rock is pretty lightweight considering its size. To be honest, I've never seen any rock like this. I'm clueless. It doesn't really look like the "lava rock" sold in pet stores...it's definitely larger.

I would just mail order some base rock, but it seems silly to pay shipping for just rock. Also, I'm not really in any kind of position to make at big purchase right now (broke student), but I love doing DIY and trying to find new ways to create a successful system.

Thanks again.

[flyhigh123]

Maybe its pumice.... its a volcanic rock that is so porous it floats.

[lophius]

I've had this problem before, I found popping it into Hot (very hot) water seemed to get alot of the air out. I left it in v hot water for about 2 hours beofre it finaly sank completely. Although I have to say that the rock i used had much larger air spaces.

It does look, from your picture, as if your rock is a very fine grain pumice

hope this helps

[Jefe12234]

It sounds like pumice to me too since it floats and can be carved, but I can't be sure. I don't know it's chemical composition, so I don't know if there's any disadvantages to using pumice. To get it to sink maybe you could try blasting it with a powerhead to push the air out of the pores.

[postalshane]

I think I remeber reading somewhere not to use that kind of rock becuase it was phosphorous and leaches bad stuff into the water. But I don't remember where I saw that, I'd keep an eye on all your levels for a while.

[RHCP]

You might want to check your specific gravity.:eek2:
time for a top off.