Hmm an 86 gallon tank seems an odd size for a tank. But anyways.
You're right, the bubble bar should be turned off when CO2 is injected during the day. You want to minimize the outgasing of CO2 and the surface aggitation that causes this degasing.
DIY CO2 for that size tank can be pretty difficult and time consuming. But I've seen people try it until they get something else. You can purchase 2 Hagen ladders from drsfostersmith.com and attach each ladder to (2) 2 liter bottles with a T-valve. Run each ladder on each side of the tank.
Though potentially pricey, you could purchase Flourish Excel and use that as a CO2 supplement for awhile, but using this product on such a large tank is not very cost effective after a few months.
Depending on your plant selection you can reduce your lighting by using only 2 of your bulbs until you can afford a pressurized setup too.
More light = more algae if insufficient CO2 and fertilization is added.