You can put the crushed coral into a bag and hang it near one of the sponge filters. What you need is water movment. As the coral is disolved you wante it to speard out into the water.
You could also add it to your substrate (sprinkle it on top). This is less nice looking and if you have fish which sift trough the substrate it might be an issue. I do this with a small amount of coral in tanks where I have shrimp or assassin snails as a way for them to get enough calcium as I have soft water.
Bear in mind that a small amount of crushed coral will raise the KH but should have minimal or no effect on pH. However, if the amount is increased, it will begin to raise the pH towards an equilibrium value of 8.2. This is one reason it is often used as part of the substrate in African rift lake cichlid tanks.
You could also add it to your substrate (sprinkle it on top). This is less nice looking and if you have fish which sift trough the substrate it might be an issue. I do this with a small amount of coral in tanks where I have shrimp or assassin snails as a way for them to get enough calcium as I have soft water.
Bear in mind that a small amount of crushed coral will raise the KH but should have minimal or no effect on pH. However, if the amount is increased, it will begin to raise the pH towards an equilibrium value of 8.2. This is one reason it is often used as part of the substrate in African rift lake cichlid tanks.
