hey everyone. So, my 10-gallon tank i set up for my son about 6 weeks ago is doing great. i picked up a ULR HannaPO4 checker. i checked my son's tank last night it was 15 - 20 nitrate {used API test} and .18 PO4 so i am doing a water change today to bring it down but last night i added 4 drops of Phosphate-E to bring the PO4 down some and then remove the bonded PO4 out in the water change. BUT.... I just checked the PO4 just now and it said .43 PO4 I don't know why it would go up after adding Phosphate-E it should at that low have gone down. Phosphate-E claims 1ml will bind up 1ppm of PO4 in 4 gallons of water so 4 drops into 10 gallons of water at .18 should have gone down a lot. this was my first-time using Phosphate-E and now I'm confused lol. I'm going to check it to my RED SEA PO4 test kit to see if that's in the same ballpark as my Hanna ULR PO4. Thanks in advance. I feel like it was either a technical error or I'm missing something in the chemistry.