Sometimes guppies end up in a new tank before the cycle is established. It happens: a “starter kit” gets set up quickly, fish are added, and then the water starts acting weird. The good news is you can still get through it safely. The goal is simple: keep ammonia and nitrite as low as possible while the bacteria catch up. That means testing, feeding lightly, and doing partial water changes at the right times.
Step 1: test daily (at least temporarily)
You need data. Test ammonia and nitrite daily during this phase. If either rises above 0, you respond.
Step 2: feed lightly
Waste is fuel for spikes. Feeding less for a short period is safer than overfeeding and dealing with toxins. Healthy guppies can handle lighter feeding while the tank stabilises.
Step 3: partial water changes when readings rise
Don’t do a 100% change unless absolutely necessary. Instead, do controlled partial changes to dilute toxins without constantly resetting the developing bacterial colony.
Step 4: protect oxygen
During cycling, bacterial activity and fish stress both increase oxygen demand. Add aeration and keep surface movement consistent.
Step 5: avoid “reset” mistakes
- don’t rinse filter media under tap water
- don’t overclean everything daily
- don’t add random chemicals hoping to “fix” it instantly
This phase ends when ammonia and nitrite stay at 0 day after day. Once that happens, your tank is stable and guppies become much easier to keep. The key is staying consistent and calm until the biology catches up.
