Floating lava rock?

[concord]

just got a big chunk of lava rock 1 question is it supposed to float and how do i get it to sink?

 

[throttle]

i've had smaller pieces float. maybe weight it down for awhile. you must have an air pocket somewhere.

 

[concord]

looks like i gotta turn airpump off then I'll put it in a bucket and wait a bit then

 

[Vapor]

Usually once all the air is out it should sink. Try moving it around in the water end for end and see if any trapped air comes out. Doubt you have to turn off your air pump, It shouldn't have an affect on it at all.

 

[concord]

AH OK THANKS MATE oops caos lol

 

[guppy]

Some types of pumice float but will eventually sink, there are two problems with pumice, first it is very abrasive so not suited for soft skinned or hilghy flighty fish, second, it tends to be acidic so watch your pH if you use much of it.

 

[Kenta]

lava rock is inert, won't mess with ph

 

[AtomixIGN]

If it doesn't sink quickly enough for you, you can drill a hole or two through it.

 

[Oddball]

lava rock is inert, won't mess with ph

Not accurate. Depends on the source and age of the lava rock. Lava rock and lava sand is used in horticulture to lower pH. Very old lava rock may be inert provided all the associated metals have leeched/eroded/precipitated away.
The best test to determine if your lava rock is safe is to place the lava rock in a bucket of water with another bucket filled with just water next to it. Test the 2 buckets pH. Repeat this test a week later. Not all but some minerals will have leeched into the water. Comparing the two buckets will let you know just how much of a change has occurred. If there has been any deviation in the readings, you can pretty well calculate how big of a swing you'll see in a year.
And, if you witness any pH change, it'll probably be a continuous leech for at least your lifetime since these processes can take centuries to stabilize (unless the leeching mineral is a carbonate mineral).

 

[Kenta]

?Everything i read states that lava rock is inert, its a by product from the smelting industry (i don't know thats what i read), especially the stuff for the aquarium trade.

But i guess it is inaccurate, if its "real" lava rock, from what i read, may affect hardness.