Someone with Discus and tank mates

cardinals can acctually be very sensative to ammoina and nitrite.

try to get your hands on some gravel or media from a well-established tank. it will help move the cycle along quicker.

What I find the best if you can take 25% of the floss or anything you can out of the other filter and put it in the new one it will cycle the tank in 7 days or less.If not take whatever media is in the other filter and sqeeze it over top of the new one.A couple handfuls of gravel will also help speed the cycle up.

AS long as you do water changes to keep the ammonia and nitrite below .25 the neons should be fine.A brislenose pleco or two is yellow and will grow only 4 maybe 5 inches and is one option you could add.

Lupin said:

Don't add any fish yet until your ammonia and nitrites are zero. Do you have plants right now? You're still far from over.

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I'm going to have to agree with Lupin here... ammonia, no matter how low the concentration, is a harmful substance to most living things. (I say most, as it can be utilized as plant food, but as far as fish, humans, etc... its no good) Are you doing water changes while cycling the tank? I know its a true test of your patience to hold off on adding fish to a seemingly empty tank, but you will thank yourself for being patient in the end. (else you may want to kick yourself if you jump the gun and add too many, too soon)

Every tank experiences a very slightly different cycling process... some take a matter of 10-12 days, and I've read about some taking in excess of 2 months. Seeding a filter for cycling purposes is great, but be cautious, this does not mean you can add a whole bunch of fish at once. This just means that with the seeded filter media, your filter can process the CURRENT ammonia levels at an acceptable rate. Increase the ammonia production, and your tank may enter a mini-cycle until such time as more nitrifying bacteria propagate to handle the added bio load. Just my 2 cents...