Helene,
Tank is 40 gallons.
I noticed when i first brought the ph down the paros colored up a lot but the chocolates hid. Perhaps they were already sick.
I noticed through all this that the new paros i have, the ones that are probably the un-named species of filamentosus are MUCH more delicate than the others i have ( blue line).
I have had them 2 weeks now and they are developing a very dark color accented with emerald green on the edges and in the fins. I believe even the female with rounded clear fins has started to develop an emerald border. The caudal is starting now to grow out the filament. Pictures to follow.
Thanks
Ryan