Please help

Do you have shells in the tank, that aren't with a live animal, such as a conch you got from a beach somewhere?

 

How about live rock?? Got any of that?

Sorry I read the post below....The lack of live rock may be the culprit.

 

It sounds like, at one point in time you had a bit of Algae. This could have been consuming all the phosphates so that they were undetectable . Now all test kits only measure inorganic Phosphates.
This is my theory.
With your current measures you have eliminated the algae you were fighting. This has left your tank with nothing to consume and therefor the phosphates are going though a the biological process of becoming inorganic. That is why you are now reading high Phosphates.
So, IMO, I would continue your normal maintenance routines and monitor. I suspect you will, over time, see your phosphates die off in short order.

J

 

Yes, we have live rock in the tank. After what we added today we have about 50 pounds of live rock. There is still algae in the tank, that is how we filter. We run water over a sheet of algae. It works very well, except the recent trouble that we seem to be having.