Tropical fish, community tanks, species care
I’m desperate for some advice. I’ve been keeping koi for about 3 years without any major issues, but over the last 48 hours I’ve lost two fish and a third is looking very lethargic. I’m worried I’m going to lose the whole pond.<div><br></div><div>The setup:</div><div><br></div><div>· Pond size: Approx. 4,000 litres (liner pond)</div><div>· Filtration: Oasis Clearwater 4-in-1 pressure filter with UVC</div><div>· Pump: Oasis 6,000 lph</div><div>· Stock: 5 koi (largest around 35cm), 3 goldfish</div><div><br></div><div>The symptoms:</div><div><br></div><div>· The fish that died were hanging near the surface, fins clamped, and appeared to be gasping.</div><div>· One had some red streaking visible in the tail fin.</div><div>· The remaining fish are sitting on the bottom. One is flashing (rubbing against the bottom) occasionally.</div><div>· No visible white spot, ulcers, or fungus that I can see.</div><div><br></div><div>Water parameters (tested just now with API Freshwater Master liquid kit):</div><div><br></div><div>· Ammonia: 0.25 ppm (this is worrying me)</div><div>· Nitrite: 0 ppm</div><div>· Nitrate: 20 ppm</div><div>· pH: 8.0 (normal for my tap water)</div><div>· Temperature: 12°C</div><div><br></div><div>What I’ve done so far:</div><div><br></div><div>· Did a 20% water change yesterday with NT Labs Tap Water Safe dechlorinator.</div><div>· Cleaned the filter (in pond water) but didn’t touch the media too much.</div><div>· Added an extra air stone.</div><div><br></div><div>The only thing that changed recently was that I fed them a few pellets last week when we had that warm day. I’ve stopped feeding now.</div><div><br></div><div>I’m seeing ammonia even though I haven’t fed in days. Is this a filter crash? Should I do a massive water change or will that make things worse? I have some Blagdon Pond Salt and NT Labs Anti-Parasite treatment in the shed, should I add anything?</div><div><br></div><div>Any help would be massively appreciated. I feel sick watching them like this.</div><div><br></div><div>Thanks.</div>
