The Tidepool is designed to take care of the first 2 parts of the nitrogen cycle; converting ammonia to nitrite and nitrite to nitrate. Bioballs do the same thing as a biowheel. They are a surface that aerobic bacteria can grow on. One type or aerobic bacteria converts ammonia to nitrite,, while naother converts nitrite to nitrate. A third type can convert nitrate back to nitrogen. That is what the nitrate filter does. It has an anerobic area where the bacteria that consume nitrates and convert them nitrogen can grow.
In the absence of 1˝-2 pounds of porour LR
/gallon of tank volume, a sump, lots of PWC
's etc. you will have ever increasing numbers of nitrates.
I already suggested doubling the PWC
's that you are doing. If that doesn't work, then do 20 - 30% per week to remove the nitrates.