Your description leads me to believe it's either Cyanobacteria (which isn't always red and can be green) or Dinoflagalettes. They can look very similar and are often confused, however, there's a real easy way to tell them apart.
In the morning, does the tank look great, with no, or very little of the slimy algae visible, but by midday, you've got "snotty strings" growing? OR, Does it look the same, from morning to afternoon, with the snotty strings always present?
Dinos die off every night. As they die, they rob oxygen from the water. This behavior, along with the fact that they're toxic, can eventually lead to the death of fish and motile inverts, especially herbivorous fish/inverts. Because they die off, every night, in the morning, the tank will look great. However, they grow very fast, throughout the day, so by midday, you'll have slimy snot everywhere.
Cyano won't appear to change, from morning to midday.
Treatment will be very different, depending on which you have.
Cyano is typically very easy to treat. Increase flow, manually remove it, by siphoning it out, do water changes and feed your tank less.
These treatments will NOT work, for Dinos.
There are two, somewhat successful treatments, for Dinos. One is more successful, but also much more difficult.
Treatment 1. Increase your pH to 8.4 and KEEP it there, for a week or 2. This requires dosing baking soda, several times per day, which makes it difficult.
Treatment 2. Turn ALL lights out and keep them out, for 5 days. On day 6, turn your lights on for 4 hours. Day 7, 5 hours. Increase your lighting period, by one hour, each day, until you're at your regular photo period.
Treatment 2 sounds scary, if you have SPS/Clams/Anemones. However, they will all be just fine. I've gone this route, in 2 different tanks, which were both predominately SPS/clams. All inhabitants were just fine and Dinos never reappeared.
Another observation....
For almost all tank problems, water changes are the best course of action. NOT with Dinos. For some reason, it's believed that frequent water changes actually fuel Dinos. Do NOT blow it around, with a turkey baster, do not do water changes, until after you've returned to your full photo period.