Hi again, cw. This may sound like my response to your previous thread.
If you have measurable ammonia and nitrites in your tank, that means excessive food is entering the ecosystem vs it's ability to cycle. That could literally be fish food. It could be a dead fish left in the tank. It could be that you're feeding properly, but have too much bio-load (typically too many fish) for your tank. It could be that you simply don't have any surface area for beneficial nitrifying bacteria to do their job. But I'd be willing to bet that you're dosing phytoplankton to excess such that they are dying and/or decomposing in the water column.
Here's the kicker and should help you understand what's been going on with your tank:
Nitrites interfere with nitrate testing. If you have measurable nitrites in your water column, your nitrate tests will show excessively high numbers. There is no reason to test for nitrates while you have nitrites in the water. You'll receive erroneously high readings every time. Ignore nitrate test results until you no longer detect nitrites.
That leads to one of three possibilities: You're overfeeding the tank (food, phytos, whatever it may be) regularly and to excess, you have too many fish for your tank size and rockwork, or the tank is simply not properly cycled yet. The latter seems improbable to impossible especially since you are detecting nitrates.
Here's what I would personally do:
1) If you haven't already, remove that GFO.
2) Stop dosing phytos. Zero.
3) Feed the fish lightly, daily. For a 2" clown, think five 1mm pellets for the day.
4) After no phytos for 2-3 days, and feeding this lightly, then test water before feeding.
If you are still detecting ammonia and nitrites, something has gone horribly wrong with your tank. If you detect zero ammonia but still detect nitrites, your tank is half-cycled but safe for fish. If you detect zero ammonia and nitrites, you've solved your problem.
Sorry if this sounds like a broken record. It might help if you post a picture of your tank.