Every now and than I get brown algae by my gravel. I had no deaths since beginning of the year except fry getting stuck between substrate. My ammonia is 0 when ever I test it, ph is stable at 8. I don't have access to any other testing kits. I do weekly or bi-weekly 20-30L water changes. I have no problem wiping the glass but just want to find out if there isn't a bigger problem.