Carbon DOES NOT leach anything bad back into the tanks. Carbon is really only active for maybe a month, doing what it was designed to do, adsorbing some impurities in the water and clarifying it. I keep and have always kept carbon in all of my filters. I have two filters on every tank over 30G and one on the smaller ones. Nitrifying bacteria will live on the carbon the same as it does on your normal ceramic media and sponges. So while I only throw new carbon in maybe once a year to help clear water after a rescape (yes I rescape at least once a year), it stays put as an established part of my biological filtration, gets rinsed along with the other filter contents when I clean my filters, and gets put back in. I could throw it out, I know it's usefullness as carbon is long expired, but I'd be throwing 1/3 of my nitrifying bacteria out and don't want to do that. The other 2/3's of the nitrifying bacteria are on my sponges and ceramic media. If I throw it out from my aquaclears, I'd just put another sponge in and have to wait for the bacteria to establish on the new sponge. There's just really no point to do that. You don't need carbon to keep your water clear and healthy if you're not overfeeding and you're doing adequate, routine water changes. I'm sure it seemed more useful years ago when people DIDN'T perform the necessary water changes that we now know are essential for the health of our fish. My tanks are spot on beautiful and my fish are beautiful, healthy, breeding and thriving and have been for years, including my discus. As are my plants, snails and shrimp. With thousands of dollars worth of fish and plants, any supposed leached toxins would have surely shown up by now. I dislike myths....a lot! Someday we'll discus how regularly and thoroughly rinsing all of your filter media in municipal tap water does not kill your nitrifying bacteria too.:grinno:
And while I don't advocate everyone raising young discus in planted tanks without fishkeeping experience and a thorough understanding of discus and aquarium/water care .....mine were all raised from 2" in this planted tank with 3 water changes weekly, then down to 2, then down to 1 now that they are adults. There are basic requirements that must be met in order to do this and not everyone can meet these requirements....IF the tank is large enough, IF you feed frequently but carefully, IF you're not feeding beefheart several times daily as the staple growth food where leftover beef fat goes uneaten and rapidly spoils in water, IF you've got healthy discus from healthy discus parents who possess the genetics to even achieve the average 6" discus size, and IF you are dedicated to this routine care for them, then you may be able to successfully raise 2-2.5" fish in a planted tank. There's a lot of IF's there. If the tank is large enough to promote proper growth, and your stock is good and it is barebottom and you change the water religously every day, yet you feed juvie discus only 1X or 2X a day...I guarantee you won't ever have a 6"+ discus. So the IF's are connected and required. Take a look at the competition/challenge going on the past year over at simplydiscus where each discus keeper got juvies from the same batch and each person is growing their discus out in a completely different manner and tank set up with differing maintenance and feeding schedules and routines, including in a planted tank without daily water changes and without beefheart. They are all equally successful in rearing unstunted fish that are very comparable in size. The IF's were all met and the keepers all had a thorough understanding of fishkeeping before they started. Here's a quick pic of my guys. 6" is average, some will be smaller no matter what you do (smaller, not stunted), and occasionally someone will get an 8" or 9" discus. It would be impossible to get an 8" or 9" discus with no genetics for it, no matter how much beefheart your feed and water changes you do. And even breeding two 8" or 9" discus isn't going to assure you 8" or 9" offspring. You MIGHT get another fish that large out of that batch, but odds are you won't. The average size for wild discus is 6" as well. It's the norm.
Turbosaurus, the first discus you got weren't fed or cared for properly period. Stunting and odd shaped discus can occur with a fish or two in any batch. It's a proven fact.
