I had my carbon for about a month which over here is normally fine as all the shopkeepers say it can last for 2 months. The only thing different between mine and cossie's is the types of fish and Cossie has fake plants and no under gravel filter
im 13 and have a 34litre aqua one tank which has:
2x Botia striata
1x tiger barbs
1x red tailed black shark
1x guppy fry
95litre marine tank
4 emerald crabs
1 hermit crab
1 haloween crab
2 sexy shrimps
I guess you can trust what people who have been doing this for like 40+ years have to say about carbon, or not. That is up to you. The statement is valid, your carbon will leech toxins back into the water, and it won't take very long for that to happen.
Now I would consider that maybe it might be worth at least trying the idea of not having it in the tank, since the fish are having a hard time breathing and you don't know why. Not having carbon in the filter will not cause any harm to your tank. At worst having it there could be harming your fish. Many fishkeepers only use carbon to pull out a medication, and then stop using it after the medication has been removed. Carbon is not necessary.
20 Long: 1 Juli Corycat, 4 red line tetra's, 3 Von Rio tetra, 1 Flame tetra 1 Rubber lipped pleco, 1 Curviceps cichlid, 1 blue tetra.
5.5ga- 1 Beautiful Betta, 1 persnickety snail
I have green things with leafs.
Note's from Bradley: "Meow." "Yes I did say meow, and I meant it."
Note from Kiera: "Can I Play with it? Can I play with it? Can I play with it? Please? Please? Please?"