Originally Posted by Darkblade48
As people have already mentioned, I would highly recommend you not using any (terrestrial) fertilizer that uses ammonical nitrogen (urea) as its nitrogen source, since it will become ammonia in your aquarium (at a pH of 8.6, there will essentially be no ammonium anion formation).
There have been people that have successfully dosed with urea, but I do not think they ever dosed when there was livestock in the aquarium.
i dose urea and NH4 with german blue rams in the tank, they also bread many times in the same tank. plant also grew better with urea and nitrate combination.