Ok first excel will work to help kill certian kinds of algea, the ones that are triggered by low co2(bbaand hair/tread). The fact that with the amount of light and no fert dosing is a big part of your problem. The gsa is a sign of low phosphates. The thread/hair algea is low co2 and ammonia, or imbalance in ferts. My advice is get a drop checker, purigen, and start dosing ferts. Use what ever method you like most will recomend EI. With your light dose 3x a week. Double dosing with excel dose not hurt anything people triple dose and things are fine. The labels are only guide lines. Plants that are affected by excel are vals, cabomba, myrio, anacheris.
