hi all Looking for some advise on what could be wrong with my red glass barb, his/her swimming is normal but having very odd spasmodic movements that appear to be triggered by light or if startled. Eats and acts normal just suddenly starting doing this erratic swimming about 1.5weeks ago. Looks like it is having a frantic seizure for about 3-5secinds. No other fish in the tank are doing this 30 gallon Tank has been established for 6months containing 8 barb fish and 1 pleco. Pleco was added 3months ago. No fighting in the tank that I have observed. Seems to have slight injury to top fin from banging into tank stuff, minor visual marking Water parameters are normal pH-8.2 normal since day1 Ammonia-.25 since day1 Nitrite-0 Nitrate -40 *only number that increased from 20 over the past month I cycle 5gallons of water every 3 weeks Any advice on what could’ve caused this?