Are you asking about increasing flow or current/water circulation? These are two very different things. I think with the Oase 250 flow should be more than adequate for your 60p. I have a fluval 307 which I really like and has similar flow in my 60p tank of around 205+ gGH. What kind of algae are you getting on your rotalas? This isn’t necessarily a sign of poor flow, but depends on the algae. Usually it can be a cyanobacteria issue that pops up in dead zones or maybe you have high amounts of organic waste in a section, but that is easily siphoned out. You can get GDA, GSA, Staghorn, BBA and other algae in area of intense flow and current. I’d look to your lights and co2 first. I’m just going off your photo here...but if you are using your drop checker for measuring co2 it is telling you that it is low. Now there are many more efficient and more accurate ways to measure co2 but it’ll give you a rough idea where you are at And yours says low co2. How long have these plants been planted in the tank? Did you dry start the carpet and add the rotalas and Anubias later? What’s the light you have over it and what’s your photo period/dosing schedule like?
I have minimal current passing through the back of my tank where my H’RAs are and they are doing great. This happens especially when you plant them in thicker bunches than what you have in your tank. If you have thick bushes of rotala, they are not going to be “Swaying In the current.” But they don’t need to be either as they are extremely efficient and fast growing weeds. How long has your tank been setup for? Flow is important, and you have a good amount already in the tank, but your algae is telling you that it is something else. Most likely a lighting and co2 issue in this case if you are dosing your ferts accordingly and not limiting ferts. Good luck.