Lava rock

[HBtank]

My FOWLR uses seriyu stone which is a limestone rock with veins of silicate. I was told it would cause terrible diatoms but 5 months in and nothing. Could be that I'll get issues later but nothing so far. It is a common rock for freshwater and a little cheaper than dry rock.

I still have my original Home Depot silica sand; it used to be recommended

I'll be honest, I kinda like diatoms.

 

[vetteguy53081]

My FOWLR uses seriyu stone which is a limestone rock with veins of silicate. I was told it would cause terrible diatoms but 5 months in and nothing. Could be that I'll get issues later but nothing so far. It is a common rock for freshwater and a little cheaper than dry rock.

Silicates with diatoms are a maybe and not always especially with good flow and low inorganics

 

[HBtank]

Silicates with diatoms are a maybe and not always especially with good flow and low inorganics

Most everything seems to like eating diatoms anyways. I find it to be very low on the list of things I consider problems, and maybe even not one at all.

I have silica sand and have always "had" diatoms. Is it truly a source of silica? I don't know but anecdotally it sure seems like it. Meaning that for 15 years the tank has had diatoms come and go as the primary "nuisance algae". I really don't mind it, and at most it is usually a dusting in the late evening. Notably I have never had cyano or dinos. I do have sponges though, lots and lots of sponges

 

[ta88brian]

This is no costs savings and will leach into your water altering ph buffering, turn water tea colored which will be acidic

Never had that problem

This is no costs savings and will leach into your water altering ph buffering, turn water tea colored which will be acidic

Not true driftwood turns water tan. My water not acidic

 

[vetteguy53081]

Never had that problem

Not true driftwood turns water tan. My water not acidic

Lava rock is comprised of volcanic material, and can be very acidic enough to damage coral and cause injury to fish due to sharp edges, It is very pourous and offers advantage to holding organims but benefits are outweighed by natural rock and impact to bacteria.
It is rare to see a tank filled with lava rock due to levels of iron and silica. Not saying it cant be used but there are better options.

 

[HomebroodExotics]

I had a 10 gallon with a ton of lava rock in it. No negative effects noticed and no water changes.

 

[HBtank]

….. Not saying it cant be used but there are better options.

I think this is the best takeaway from this thread.

 

[Slocke]

Volcanic rock being igeneous won't break down into the water like the limestone rocks we use. However they may contain unknown elements within them that may leach. Also one reason we use limestone is that it naturally adds alkalinity to the water. So though they won't decrease the Ph themselves they won't prevent Ph changes. This may cause the natural Ph to be lower and/or more susceptible to Ph swings.

I've heard multiple people such as The Everyday Aquarist who mention algae issues when using lava rock. That suggests to me that it perhaps leaches elements such as iron which is often a limiting element in algae growth in the ocean.

I'd also worry about fake lava rock or lava rock that has been treated with chemicals. With that in mind I'd use lava rock specifically for aquariums rather than for landscaping and other uses.

 

[sfin52]

I've always wondered 'why not?', there are many natural reefs in the world built on the bases of volcanoes, ie, lava rock. If nature does it, why don't we do it in our tanks?

Be ause the ocean is huge and can dilute by tides and storms. Look at all the coral growing on metal. Would you place a peice of metal in your tank.