BobbyBray, that rainbow was probably showing you that the water in her tank was not fine. By doing the large water change with appropriate pretreatment, the fish may have been spared and tomorrow's water change could put it on the road to better health.
The next thing that you could do is put your filter on your GF's tank. That way any bacteria that you have in your filter will be able to help hers and after 2 or 3 weeks, both filters will be quite ready to go it alone on your two tanks. Contrary to what we normally say, we don't cycle tanks, we cycle filters. By using a fishy environment with at least a partly cycled filter, you will get a head start on cycling your own filter.
If your GF has a cartridge type filter, they are especially hard to share media with. Being a rigid cartridge, they don't work very well unless they stay intact. That means that the usual approach to cloning a filter does not work well in that situation. I have a few of them in different tanks and just ignore that kind when I want to clone a new filter. Instead I use the media from a canister because it will work fine after I remove 20 or 30% of the media.
The next thing that you could do is put your filter on your GF's tank. That way any bacteria that you have in your filter will be able to help hers and after 2 or 3 weeks, both filters will be quite ready to go it alone on your two tanks. Contrary to what we normally say, we don't cycle tanks, we cycle filters. By using a fishy environment with at least a partly cycled filter, you will get a head start on cycling your own filter.
If your GF has a cartridge type filter, they are especially hard to share media with. Being a rigid cartridge, they don't work very well unless they stay intact. That means that the usual approach to cloning a filter does not work well in that situation. I have a few of them in different tanks and just ignore that kind when I want to clone a new filter. Instead I use the media from a canister because it will work fine after I remove 20 or 30% of the media.
