A 35g hex is not suitable for Balas. They will get up to 12" a piece and need a very long lateral tank - not a tall tank - a minimum of 6ft long! They will rapidly outgrow that 35 and may well begin to injure themselves crashing about and into the glass. This is how they should be kept, this is a 10ft tank!
http://www.youtube.com/watch?v=gfbspqOI2sw
Rehome the Balas. A 35g would be suitable for a single Angel and a few rummynose tetras or corydoras (mid-bottom dwelling fish to keep out the way of the Angel). The trouble with hexes is that due to their shape they have only a fraction of the stocking space of long tanks - fish are lateral swimmers!
