Magnesium Sulphate instead of Seachem Equilibrium

Hi,
I'm trying apply EI. Checking my Gh and KH levels in order to achieve EI targets, tests showed me readings about 9°GH and 4°KH. I was adding MgSO4 and CaCl2. In order to modify the magnesium and calcium dose and reach the 5°GH recomended by Tom Barr, i need to know how much MgSo4 and CaCl2 should be added. I live in Colombia, so Seachem Equilibrium isn't easy to find. Tap water in my city is very soft. My aquarium volume is 55 US Gal.

I'm having trouble with algae, too much light maybe? (4x54wT5HO 8 hours/day) (Co2 is about 35 ppm). What do you think about turning on 3 54wT5 9 hours/day, and 3 more for 3 hours?

Regards, sorry about my english.

 

Thanks for replying. I'm following your suggestions, so i did a 50% water change and reduced the light to 2 54wHO bubls turned on for 8 hours. During the day, 2 more bulbs turns on for 2 hours, so the photoperiod is: 108 watts/3 hours, 216 watts/2 hours, 108 watts/3 hours. EI weekly dossing targets are 30ppm No3, 30ppm K, 3ppm Po4, 0.5ppm Fe. The algae growth seems to be stopped and plants are healing their deficiencies; beore i started EI, fast growing plants got pale and almost white new leaves. I got a question, can Magnesium and calcium relationship lead to a green dust algae?
Regards