rocks for tank?

[da_xiong]

Hi all,

May I ask what kind of rocks are suitable for aquarium as in, it would not affect the water parameters, as I read that some rocks can affect the ph and hardness of the water

I intend set up a nano 1 ft tank with some foreground plants like glosso etc with some danios and rcs, so I would prefer it not to affect too much of the ph and hardness...

I have a few in mind, but not sure if it actually can work, so I need some advice from seniors here haha.

the few i had in mind are

1) lava rocks
2) dragon rocks
3) slate

and also, where can I get these nice rocks? and also I notice most shops don't really know what we are talking about as in they know things in their own terms, so sometimes due to lack of communication can get the wrong thing, something I worry here for rocks, as all rocks looks the same to me haha... maybe slight differences...

would appreciate if any seniors can advise thanks! haha

[Urban Aquaria]

Most rocks will affect pH and hardness in the water, but how much and how fast will depend on the volume ratio of the rocks vs water (a tank with only 10% of rocks will be alot less affected than if the tank that is 50% filled with rocks), and the frequency of your water changes (more and larger regular water changes will slow down the effect).

One way to test is to get a few pieces of the rocks and soak them in a small tub or bucket of water, test the water before and then 1 week after, see if there are any changes, if there are none or very little measurable differences, then those rocks should be good to use.

That being said, if you are keeping adaptable fauna like danios and RCS shrimps, the shifts in water parameters from rocks shouldn't be much of an issue as those fishes and shrimps can adapt if the changes are gradual over a period of time.

[SunDragon]

Tested my lava rock, TDS reading increases by 10 over 4hrs duration in a 1.5litres container. Decided not to use it.

[Urban Aquaria]

Tested my lava rock, TDS reading increases by 10 over 4hrs duration in a 1.5litres container. Decided not to use it.

TDS increasing by 10ppm actually isn't much... probably just some residual micro dust or fine particles in the rock.

Just for comparison, using declorinator for treating tap water can already raise TDS by 5-10ppm, dosing ferts and supplements increase TDS even more.

Lava rocks are generally not completely inert anyways, there are lots of "stuff" trapped in their porus structure from all the previous environments they were in.

But if the TDS increases by 100-150ppm within just a short time, then there'll be cause for concern.