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Rock ID...sponge?

2952 Views 8 Replies 5 Participants Last post by  chagovatoloco
I picked up these rocks at a local lanscape supply yard.
I'm not sure what they are or if I should use them in the tank.
From their website it seems they are either sponge rock or holey rock

Sponge rock...

Holey limestone...

Anybody know anything about this rock or where it comes from?
Would it be safe for my tank? I took them to the car wash and they had a lot of rust on them that washed, and washed, and washed. I think I got them pretty clean. And no, I didn't use any soap on them! I hope they wouldn't turn the water rusty.
I would like to use them in a iwagumi scape.
Here are the ones I found...

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People like this hardscape with these rocks? Suggestions welcomed before I do the plantings. Whats in there will be coming out and I'll be planting hairgrass, blyxa, and HC. Maybe a few other things.

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If they were rusty, they're probably going to start leeching heavy metals into the water. Have you tested your gH and kH since adding those rocks?
Why only three rocks?

No I havn't tested the GH and KH. I'll test after a few days...just did a big water change. Not too worried about heavy metals because I do weekly 50% water changes.
Those rocks should be fine as long as you don't want to maintain soft water.
I think the smaller ones would get lost in the aquascape when it grows in, just an opinion.
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