Oh my... yeah, that's definitely red algae, also known as cyanobacteria. It's really not an algae, but is a bacteria that feeds off of excessive nutrients in your tank and loves water with not much flow. Yes... it's not good to have in a tank.
Here's a good starting point on researching the stuff...
And here's a good condensed "how to get rid of" article...
Look at #9 on the list... "Quit using additives such as coral growers". I'm not familiar with "Reef Plus" but it looks like it's Seachem's version of a coral supplement with vitamin, trace elements, etc. I don't see any corals in your tank to start with, so you definitely don't need that stuff. Even if you do have corals, frequent water changes (weekly or biweekly), good water parameters, and good lighting in addition to occasional feeding if the coral requires it, is all you need.
If you post your water parameters (ammonia/nitrite/nitrate, as well as pH/alk
and phosphates) and give us some more background about your tank (number/type of powerheads and pumps, water change schedule, type of water you use to start with) I'm sure folks will give you some suggestions as how to rid yourself of it.