Cycling builds the bacteria that turn toxic ammonia into safer nitrate. Avoid these mistakes so guppies go into stable water.
What to avoid
- Rushing fish in: add fish only after ammonia and nitrite read 0 for several days.
- Overcleaning: never rinse sponge media under the tap; chlorine kills the colony.
- Overfeeding the cycle: too much food rots and stalls growth; a pinch every few days is enough.
- Ignoring KH: very low KH (< 2 dKH) can cause pH crashes; add a little crushed coral if needed.
- No test kit: strips miss details — use a liquid kit for ammonia, nitrite, nitrate, and pH.
- Changing 100% water mid-cycle: big changes reset progress; do smaller changes unless ammonia/nitrite spike high.
- Adding too many fish at once: start with a small group, re-test, then increase stock gradually.
When in doubt, seed your filter with media from an established tank and keep the filter running even during water changes.