We are currently conducting research involving tests for high level phosphates, but have yet to find tests that we're happy with. Field tests that are currently available on the market can you let you know if phosphates are present, but can't tell you to what extent they are present. In other words, they're not quite sensitive enough to be useful! Also, many of the field tests require you to handle reagents that can be toxic, and that makes disposal difficult, meaning they wouldn't be safe for kids to use. We are watching this space closely, and working with partners to see if this can change.