Proper flow can be measured?

[Cubeforfun]

So I've been around off and on for awhile. I've heard a lot of GPH flow myths and "general rule of thumb" posts. But what if you take the sump/refugium aspect out of the equation? I'm talking about what's going on in the tank. Directionally, intermittent flow and how much and heavy your corals are being supplied by good water/nutrient supply from your current setup. How do you know what's optimal? How much time do you soend tweaking this factor or your system?

Example:

I have a 45 gal. Cube with 2 vortech MO10's on the back wall facing the front glass, one one the far left and high that breaks the surface and one on the far right middle placement, both of which changes modes periodically throughout the day from my reef link. But how do I know that this is the best setup and placement? Some times in lower flow modes I can see the film/gas build up on the surface of the water. But don't SPS/LPS/ softies (I have a mixed reef) need a break sometimes?

Anyway, my point is, isn't this just trial & error or is there a way to gauge how much current is actually in the display tank and a formula for a correct amount of water movement?

Thanks for reading and responding. Happy Reefing

[Ron Reefman]

You have to consider the flow from the sump back into the tank in your total flow calculation.

Take your vortech max and min flow numbers and average them for a basic calculation.

Do corals need a break from flow??? If you are concerned, consider reducing the flow at night. Some reefers do, many don't. I don't, but I have a big system 400+ gallons and mostly sps corals.

Yes, a lot of flow issues are trial & error. My take on it is the more you can vary it, the better it is for the entire system. Every pump in my system (2 DC12000's, Maxspect 150 Gyre, Jebao wp40) have flow that either varies up and down, or moves the output, or both!

[mcgyvr]

Until corals learn to talk we will never really know the "best" flow..

But by watching how each coral does in the spot you have currently placed it may be a start.. If its closing up or blowing over or having the skin just blown right off it then thats the wrong flow for it..

If algae/sand/detritus,etc.. is collecting on it then thats not enough flow..