Ammonia spike from overfeeding? Fix it fast

An ammonia spike from overfeeding in a new tank is a genuine emergency — fish can go from stressed to dead within 24 to 48 hours if ammonia stays high, so you're right to want immediate help. Before we get into the fix, quick questions: what size is your tank, do you have a test kit confirming the ammonia reading and at what level, and are your fish showing symptoms yet — laboured breathing, sitting at the bottom, red-tinged gills?

Okay — 1 ppm ammonia with a fish gasping at the surface means you need to act in the next few hours, not tomorrow. Goldfish are also heavy waste producers, so four of them in a 60-litre uncycled tank is a lot of load. Your first move right now is a 30 to 40 percent water change using dechlorinated water matched to tank temperature — this dilutes the ammonia immediately. But water changes alone won't hold it, because the tank has no established beneficial bacteria yet to process ammonia continuously. That's where a detoxifier comes in.

Yes — get API Ammo Lock. It's widely available on Amazon UK and most fish shops, and it works by chemically binding ammonia into a non-toxic form that your test kit will still detect but your fish can no longer absorb through their gills. That buys you critical time while the tank starts to cycle. Dose it tonight after your water change, then redose every 48 hours while ammonia remains detectable. It won't remove ammonia permanently — only a cycled tank does that — but it will stop it killing your fish right now.

Stop feeding entirely for three to four days — there is no debate on this. The decomposing food already in the tank is producing more ammonia than your fish need from new food right now. After four days, feed a tiny pinch every other day, only what they eat in two minutes, nothing more. Keep dosing API Ammo Lock every 48 hours and doing 25 to 30 percent water changes every two days until your ammonia reads zero and you start seeing nitrite appear — that tells you the cycle has begun. Realistically that process takes three to six weeks in a new tank.

There is — Tetra SafeStart Plus is a bottled bacteria product that actually works and is available on Amazon UK. You add it after a water change and it seeds the tank with the live bacteria that process ammonia and nitrite. It won't give you an instant cycled tank, but it can cut weeks off the process. Use it alongside the API Ammo Lock, not instead of it — right now detoxifying what's already in the water is the priority, and then the bacteria product helps build the long-term solution. Do the water change tonight, dose Ammo Lock, and order both if you can.