How soon to do nitrite test after water change?

Nitrite spike not helped by water change?

Is there a set period of time to test for nitrite, after having done a water change?

I'm encountering a mini-cycle after a filter failure that occurred just after moving to the new tank ... got a nitrite spike, and I want to make sure I get accurate readings.

The reason I asked, is that water changes are failing to reduce the nitrite levels.

Do I need to clean filters, additional gravel vac, etc? I don't want to do anything to ruin an establishing bacteria colony, but of course I can't let the fish suffer thru high nitrites.

Here's the whole sequence of events, moving from tank to tank, with equipment changes ... please tell me where I need to turn next ...

• Day 0 - set up 45g with biowheel filter from existing tank
• Day 2 - ammonia .5, nitrite 0, nitrate 5.0 - begain 25-50% daily water changes
• Day 3 - added Filstar XP1 (foam, Bio Chem Zorb, polishing filter)
• Day 4 - ammonia .5, nitrite 0, nitrate 5.0
• Day 9 - biowheel filter failed; replaced with new Aquaclear 50 (biomax & foam)
• Day 10 - ammonia 1.0, nitrite 1.0, nitrate 10.0
• Day 12 - cleaned Filstar; rinsed media, removed Bio Chem Zorb bag
• Day 12 - ammonia 1.0, nitrite 1.0, nitrate 10.0; performed 50% water change
• Day 13 - ammonia 1.0, nitrite 1.0, nitrate 10.0; performed 33% water change
• Day 14 - ammonia <.5, nitrite 1.0, nitrate 10.0; performed 33% water change
• Day 15 - ammonia <.5, nitrite 1.5, nitrate 10.0; performed 33% water change
• Day 16 - ammonia <.5, nitrite 1.5, nitrate 10.0; performed 50% water change
• Day 17 - ammonia 0, nitrite 2.0, nitrate 10.0; performed 33% water change
• Day 18 - ammonia 0, nitrite 2.0, nitrate 10.0; performed 50% water change
• Day 19 - ammonia 0, nitrite 2.0, nitrate 10.0; performed 50% water change

FWIW I am using tap water, close as possible to the existing tank temperature, and using AquaSafe as water conditioner.

Thanks!