Good grab on the aro man!! 30$ is a sweet deal!....
I do have a warning for you if you choose to listen... crushed coral will definitely raise the Ph in your tank to above what is needed for a silver arowana and you'll never be able to lower it without dosing! Yes crushed coral is beneficial,but not as a substrate. If I were you, I would immediately switch that out with something that looks like it and just use a media bag half filled with crushed coral and put it in your filter. That's where the Benifits will be. I use duckweed in my tanks that eat Ph like crazy and run crushed coral in the filters to buffer the Ph. My Ph is 6.9 to 7.0 Always. Never changes.
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