Since you are still reading 5PPM with a 2 to 1 ratio you are at 15PPM+. You might want to try a 3 to 1 ratio of distilled water and the water you are testing (multiply by 4 for the result), this will get you to read up to 20 PPM. If you still get a reading of 5 do a 4 to 1 ratio. Eventually you should get a reading of less than 5, this should be close to what your levels are. (Not sure how much you can dilute and still get a good reading).

I hope that makes some sense.

So far I have not had to deal with algae, but from what I have seen here, you want to keep it at shock levels until you have won the battle.

I agree with getting a FAS-DPD test kit if you can find one locally, or you could order one on-line.

And yes, it is better to laugh than cry.

Oh yeah, darn Leo's, no patience I tell ya. LOL!