Urk. You changed the filter and carbon? Keep a VERY close eye on your water parameters; nitrifying bacteria lives in the carbon and filter media (thats most likely what the brown goop was) and you may have removed most of it when you took out the filter. The smell....did it smell like fresh wet dirt? Or something else? Just for future reference, rinse the filter out in the water you remove from the tank during water changes. This way most of the bacteria will remain.
Also, smack daddy's hands for me LOL. You really don't want to add new fish to a tank with ammonia levels registering. Don't forget, the fish will add their own contributions to the ammonia (both by respiration and digestion), and you will have to feed them too, so more food into the tank. Catfish, especially algae eating ones, add a heavy load to the tank (they are the poopingest things I've ever seen!). In fact, make daddy pop on here and read up on all the research you've been doing.
Btw, what sort of albino cats? Bristlenose? Love them; cool lookin fish! Do know tho, they get to be about 6 inches each; 2 is too many for a 10g (plus there won't be enough algae for 2 in that size tank). Also, you'll need to pick up some driftwood for em; plecs require the lignin in the wood for digestion.
Lastly, a question. What sort of filter are you using? I never thought to ask before.
Also, smack daddy's hands for me LOL. You really don't want to add new fish to a tank with ammonia levels registering. Don't forget, the fish will add their own contributions to the ammonia (both by respiration and digestion), and you will have to feed them too, so more food into the tank. Catfish, especially algae eating ones, add a heavy load to the tank (they are the poopingest things I've ever seen!). In fact, make daddy pop on here and read up on all the research you've been doing.
Btw, what sort of albino cats? Bristlenose? Love them; cool lookin fish! Do know tho, they get to be about 6 inches each; 2 is too many for a 10g (plus there won't be enough algae for 2 in that size tank). Also, you'll need to pick up some driftwood for em; plecs require the lignin in the wood for digestion.
Lastly, a question. What sort of filter are you using? I never thought to ask before.