I've finished cycling my 40-gallon AIO reef tank and added five corals about a week ago. They are hardy species: two acans, one frogspawn, one leather and a fungia. All appear ok, and have eaten mysis when I target fed them. Ammonia and nitrite are zero, nitrate is 4 or 5, pH is about 8.2, alkalinity is 8.5, magnesium is 1240, calcium is 420. The nitrate had been way up during cycling and then came down and has been very steady at about 4 to 5. My concern is phosphate. It seemed to be fine, hovering around .03 and .04, then suddenly spiked up to .34 two days ago and then .28 today. This happened after I target fed for the first time. If it's coming down, it's not coming down very fast. I have two caddy/cartridges that slide into the built-in sump in the back and I have Chemi-Pure Blue with a phosphate sponge/pad in one and Seachem Seagel with chaetomorpha in the other. Yesterday I did a 20 percent water change. From everything I've read, this all should control the phosphate, and seems to be keeping the nitrate in check. The nitrate did not change after feeding. Does this make sense? Can anyone hazard a guess as to why phosphate would shoot up like that when nitrate does not indicate any change? Is there anything else I should be doing to address these levels? Does anyone have experience with phosphate removers such as Brightwell's Phosphate-E? Basically I'm wondering how worried should I be, and how urgent this situation is. Thanks for any help or advice you can offer!