This might not be a problem - just a behavior I don't know about.
My 2 percula (false) clownfish are madly swimming from one corner to the other, making a down, then upward swoop along the way, on the same end of my 75g.
Once in awhile, one will swim clear to the other end, then race back, joining the other for more back and forth - its almost like they're racing.
Maybe they're playing - anyone else have crazy clownfish?
Water is good (still cloudy as mentioned in another post), but ammonia at zero, nitrates betwen 10 and 20, nitrite close to zero (just barely registering above, not quite up to 0.25). SG
1.022 and temp 78 (both stable for some time).