WANTED: Natural calcium stones

Anyone used seachem safe to stop nitrite

Does anyone know what to put in a Koi pond to get rid of string algae Having a hard time finding something safe for Koi

What dechlorinator do people use a liquid or a charcoal canister. Any recommendations would be really helpful thanks

Hi all just got these stones from the internet they say they are natural calcium for shrimps is it ok to put it all in my tank or should it just be 1 bit thank you