Visualizing Flow

[Dana Riddle]

Now that I'm back from Wyoming to see the eclipse... If you've ever dived on a natural reef that has a fine size bed of sand, you've probably noticed rippled patterns. That's what I'm seeing in the new 90-gallon tank sand, and I measured the water velocity with a Marsh-McBirney electronic water velocity meter. The flow rate is a tad over 6" per second, which is what I measured on Kona, Hawaii reefs when the water was calm. So, if your sand bed isn't moving around (ripples, little 'tornadoes') you don't have what corals can experience on a calm day. Oh, the sand is CaribSea's Fiji pink sand (grain size perhaps 1/2 mm.) Their crushed aragonite with a much larger grain size is not moved at a velocity of 6"/second. I've always wanted to investigate ways to visually judge water flow, and this is a very small start. Experimental protocols are being developed to investigate how colony size (or more correctly, porosity of the coral's interstitial spaces) affects water flow.

 

[Diesel]

Following!

 

[ReeferMaddness843]

I've heard the method of tying a piece of small ribbon to a chopstick and checking different areas may help for a start. At least to make sure there are not any dead spots.
Kinda like the tassels on a fan to show its on. Not a scientific method by any means, but will give a basic visual baseline.

 

[trevormass7]

Following!

+1

 

[Fishhands]

I love reading your articles. Very informative. A few questions on my mind abour this...What pumps are you using? What speed? (im assuming they're variable) How far from them are you taking measurements? This is a great idea to make better adjustments to our own tanks. The only numbers we have are turnover rates which are anectdotal. Ive heard anywhere between 30-60x volume. There must be a sweet spot.

 

[Dana Riddle]

I love reading your articles. Very informative. A few questions on my mind abour this...What pumps are you using? What speed? (im assuming they're variable) How far from them are you taking measurements? This is a great idea to make better adjustments to our own tanks. The only numbers we have are turnover rates which are anectdotal. Ive heard anywhere between 30-60x volume. There must be a sweet spot.

Thank you! Lab work can be boring so it is nice to hear a compliment! I'm using a Tunze 6255 (tested and run at full speed to produce ~7,100 gallons per hour) and a Danner return pump with flow accelerator (about 400 gallons per hour.) True tank volume is about 80 gallons, so 'turnover' is about 90x hour. The fine sand bed has been moved towards the middle of the tank with natural looking 'ripple' patterns. Coarse gravel is not moved at the velocity of about 6" second, which is measured about 40 inches from the pump. I'll post some photos in my tank/lab build thread as soon as things slow down a bit.

 

[Diesel]

Now Dana, with or without the use of sand You will still get the same effect, right?
The fine sand is only for you to see if the pumps and flow gives you this effect.
I've used many pumps and lots of different sands in the past but still of today I never got to see that ripple effect in my tank.
Well, twice maybe but I had no rock in the tank and one frag tank with no pumps what so ever but just sitting outside in the wind gave me the ripple effect on the sand after a few days.

 

[Dana Riddle]

Now Dana, with or without the use of sand You will still get the same effect, right?
The fine sand is only for you to see if the pumps and flow gives you this effect.
I've used many pumps and lots of different sands in the past but still of today I never got to see that ripple effect in my tank.
Well, twice maybe but I had no rock in the tank and one frag tank with no pumps what so ever but just sitting outside in the wind gave me the ripple effect on the sand after a few days.

The effect in the sand was unexpected since the goal was simply for the tank to have 'sufficient' flow. The tank has as much rock and sand as it is going to have. We'll see how the first frags do - I'm not certain that a continuous velocity (as opposed to surge pulses) this high is beneficial. The plan is to go by the LFS and get some corals tomorrow. Stay tuned!

 

[Donovan Joannes]

Just like what happens at the dessert with all the ripples, I think the water flowing close to the sand surface at certain speed in single direction will create that effects. In our reef tank, we are creating turbulences.

 

[Fishhands]

When its this kind of lab its not really work, and if staring at your tank for x# of minutes is broring than consider me bored out of my mind. Only one pump? Why not two at half? Do you like to leave it on full blast or do you use modes? What is the orientation(front,straight across,surface, or sand) and location? Surely the flow closer is greater than 6" per second as this effects coral placement. Im sure pics will answer some of this. Just a bit excited about this. So many questions. Im so nerdy.

 

[Dana Riddle]

A quick and dirty photo of the new 90-gallon. Note the flow has pushed the sand towards the middle of the tank, leaving only crushed coral at bottom left (where the flow rate is about 6" per second.) At top left, there is an air vortex created by the flow from the Tunze. The return pipe from the Danner pump with the flow accelerator is at top at about 11 o'clock. Just added the first frags a few minutes ago. We'll see how they do.

 

[Fishhands]

How are the stucks doing? Has the flow remained.

 

[becks]

I assume this just for SPS? As my LPS would be blasted?

Do you have any figures for lagoons Dana?

 

[Fishhands]

I figured even for sps this was high. Too much flow closes the polyps on even my montipora

 

[JBNY]

Hi Dana,

I think one of the biggest challenges with flow is sand. In the picture you have shown, I think if you leave the tank for a few more weeks you will see the sand star to be pushed even more to one side and the tank bottom being exposed. I've been a big proponent of lots of flow in SPS tanks for years but for me it's always a balance between enough flow for the corals and not too much that all the sand is either blown into the water column or back into one side of the tank.

-Joe

 

[Shon]

I've always wanted to investigate ways to visually judge water flow, and this is a very small start.

Silly noob q/thought..

Would you be willing to dose bioluminescent phyto?
https://empco.org/bioluminescent-algae/pyrocystis-fusiformis.html
I bet you can visually see water flow that way.

 

[revhtree Verified Admin]

Thanks for the info Dana! Just thinking about flow today!

 

[Dana Riddle]

Hi Dana,

I think one of the biggest challenges with flow is sand. In the picture you have shown, I think if you leave the tank for a few more weeks you will see the sand star to be pushed even more to one side and the tank bottom being exposed. I've been a big proponent of lots of flow in SPS tanks for years but for me it's always a balance between enough flow for the corals and not too much that all the sand is either blown into the water column or back into one side of the tank.

-Joe

Hi Joe, Can't argue with your successes, so I won't . I'm not seeing any flow-related issues and the sand migration seems to have stabilized. The fine Fiji sand was laid over coarse aragonite sand which is staying in place but I'll keep an eye on it. Hopefully I can keep the as high as it is- there isn't a chance that any fish waste will ever accumulate on/in the sand bed. The issues I'm having are due to too much light generated by the inexpensive Chinese black box. A couple corals are lightening up a bit too much for my taste (theirs too for that matter.)

 

[Dana Riddle]

Thanks for the info Dana! Just thinking about flow today!

The flow 'turnover' in the tank is about 120x its volume, yet I'm not seeing any problems - polyp expansion is good on all corals although I need to move a Euphyllia 'torch coral' to a spot with a little less flow. Now to get the lighting dialed in!

 

[Fishhands]

Dana, fwiw i have a Chinese led and i have mine dialed way down. Whites are at 5% this includes red and green. Blues at 25% and ramp up to 30% for a few hours. Two purple leds are at 20%. When i turn up any more than that tissue is receding away by the next day. Tank is only 16 inches deep and lights are 11 inches off the water. Ive heard of people running them way higher, but i dont know how. It is a beast. Way to powerful to run at max or even near full power.