Platies, Mollies, or Tetras for re-stocking tank

Question
I have a 60 gal. hex tank, with an undergravel filter, Aqua-Clear 3 stage filter, and an Aquaripure denitrifying filter. Vacuuming gravel and water changes are difficult for me but I can manage 20% water changes and vacuuming about one a week.  The tank developed "old tank syndrome" and I have finally got it back to 0 ammonia, 0 nitrites, 20 ppm nitrates.  My water is naturally very hard and has a pH of 7.8.  I want to re-stock the tank (at the moment it has 1 Chinese algae eater) and I'm deciding among tetras, platies, and mollies (prefer just one breed).  I can adjust the pH, but can't do much about the hardness--of the three types of fish, which one would you recommend as most likely to stay alive? Or would  you recommend a different breed entirely? I should mention that the tank is fully planted.

Answer
Hi Eleanor,
Actually, I think your aquarium is just about perfect for all those fish you listed. Tetras, Platies, and Mollies are all hardy for the most part and they should do perfectly fine in your current pH of 7.8

It's actually more harmful to try to change your pH because the resulting flucuations from trying to adjust it can be very stressful for fish.

I really hope this helps!
You are doing a really good job with your aquarium-keeping and I wish you the best!
Karen~