A good references for current's effects on attached algae on plants:

John A. Strand, Stefan E. B. Weisner, Wave exposure related growth of epiphyton: implications for the distribution of submerged macrophytes in eutrophic lakes, Hydrobiologia, Volume 325, Issue 2, Jun 1996, Pages 113 - 119

This study showed that intermediate wave action had a positive impact on plant growth, which a negative impact on periphyton(attached algae).
Low wave action had a positive impact on perinphyton but intermediate affect on plant growth(can you guess why? No/less CO2 with lower wave action). high wave action rips the plants up and they cannot grow there and no plants nor periphyton was found at these sites.

In general, the highest biodiversity is found where there is an intermediate disturbance level. This can be seen in the intertidal zone of marine systems and most anywhere in ecology. The intermediate disturbance hypothesis is the term used to describe this effect(Connell 1978). It is wide ranging and explains why some locations have high or low diversity of species.

This one is good as it shows that simply swirling a plant around it water for 90 seconds can remove 80-90% of the epiphytes growing on it.
So fluffing a tank up every few days can help.

Zimba, P.V., &Hopson, M.S. 1997. Quantification of epiphyte removal efficiency Zimba, P.V., &Hopson, M.S. [1997] Quantification of epiphyte removal efficiency from five submersed plant species. Aquatic Botany 58:173-179.

ref:
Connell, J. H. 1978. Diversity in tropical rain forests and coral reefs. Science 199: 1302-1310.

So what might we conclude here?

Good current is helpful.
It physically removes algae and makes it hard for them to attach and colonize.

It also allows the CO2 mist to get blasted all over, it also reduces the boundary layer around leaves so the plant has more access to the nutrients in the water column.

Not too much though, but an intermediate amount.

Regards,
Tom Barr

Would those wave makers used in saltwater tanks be a good way to do this,
Or just hooking up an extra powerhead and running it every X hours have the same effect?

I would tend to prefer a smaller power head left on all the time.

Most of my tanks are filtered by a powerhead mounted on a Hydrosponge, and this works fine in any of my planted environments.

...now if only I could incorporate a fine pore diffuser into the Hydrosponge I might have all my bases covered....

Yes, those large wide dispersal powerheads are good for this.
You need to make sure you do not blast the pklants out of the substrate though.

I can see algae form where there it less current on the glass, and nmopne near the outflow blast, and this will happen when the algae bloom is strong also.

Regards,
Tom Barr

Limewood diffusers are very good FYI also.

Regards,
Tom Barr

Wow! Very cool studies Tom. Definitely the kind of info that won't be found anywhere else.

When you suggest "not too much" but an "intermediate" level of current, we should err on the side of too much rather than too little, shouldn't we? It sounds like there's quite a bit of room for error on the high side before things would get to the stage of ripping up plants. As long as fish and plants aren't being blown around the tank....

Also, it sounds like using a diatom filter while fluffing up the tank might not be a bad idea either.

Yes, very true on both points.

Diatoms do work well for polishing.
Medium current means some surface movement, but no white caps
Good even flow but not that much plant movement. Gentle swaying.

Still, a good fluffing does good.

Regards,
Tom Barr