I've just finished putting the stones onto the liner on my fishpond and a trowel full of cement fell in! When will it be safe to put fish in or will I have to change the water now? I was planning on planting it up first anyhow and letting the plants get established.
Cement contains large amounts of calcium and magnesium, which act as alkaline buffers when dissolved into water, like a pond. Because of this, you're likely to see your pH skyrocket for quite some time. If there's any way you can get the cement out of the water, that would be best. If not, you're gonna be dealing with an abnormally high pH for some time, which isn't necessarily a bad thing, as Goldfish and Koi will do just fine under such conditions. Regardless, I'd try to flush out as much of the water as possible before getting any fish.
