Fishless Cycle Help

What time do you do the tests in the morning and at night? Are they 12 hours apart?

If you do the night test before the water change and it shows 0ppm for both ammonia and nitrite, then it is already done. Since we use 24 hours as base for how much ammonia it can convert (daily).

You might have trouble to convert Otocinclus Catfish to eat zucchini. I have had luck feeding them Hikari Algae Wafer.