odd behaviour

[fonze]

Ok so here's what's happened. Yesterday I replaced my external filter but left the internal filter in place. Tank is a 125 litre with a fluval u3 internal and now a fluval 306 external. I put the bio noodles from my old ext in the new one and left the internal in place. Molly's are just hanging about at the bottom of the tank and the black phantoms are turning on their side. Tested water this evening ammonia 0, nitrite 0, nitrate .25. Any idea why they would be doing this?

 

[librarygirl]

Hm, well your levels seem good. Are you using strips or a liquid kit? Do you run Co2? Maybe check the filter connections, make sure nothing is off and it's running ok. Do a 50% water change just in case something got into the water that the fish don't like. Did you rinse the new media out before using it, if you used any new media with the new filter? Maybe some packaging stuff got into the tank. I'd start with a water change and keep an eye on parameters, see if it helps.

 

[fonze]

Done a 20% water change this evening after testing and posting on forum just as a matter of course, the new media was left to soak in the "dirty" water from the water change on Saturday for 24 hours. New sponges squeezed and soaked as well. Water test kit is a Hagen liquid test kit (nutrafin). I am running an air curtain and I thoroughly washed the new filter housings and baskets with warm water and left them to drip dry over night before installation.