If you haven't kept heckels before, I would advise you to not mix them with other species.
Keep things very simple for yourself to start: barebottom tank, lots of clean water with stable params, and sponge filtration.
Learn to keep them happy and healthy before you introduce a bunch of other variables.
I have been keeping heckels for about 2 years now. They are great fish and hardy as horses. However, they also have very specific needs. I've found that mine seem to do best with slightly softer water and didn't really appreciate my tap as much. So now I use an RO mix and keep their TDS around 120. I feed them a variety of foods and keep their tank clean.
hth
-Ryan