Reef Salinity

[tmz]

Re: a million gallon per day water change per cubic meter on a natural reef.
I have read that as well and noted it. I find it a useful way to get a sense of the vastness of water in coral's natural environments and the amount of new ocean water corals in nature receive as compared to a reef tank. It aslo helps in understanding the why various water parameters are so readily constant in natural reef environments and difficult in closed systems.

I was skeptical of this number but after thinking about it, it seems very reasonable.

To move a million gallons of water per day through a sqaure meter window would require movement of about 2 inches per second ( about 5 cm per second).

The math:
2 inches per second x 86,400 seconds per day=172,800 inches per day.
172,800 inches divided by 39.27inches per meter=4,400 meters per day.
4,400 cubic meters @ 233 gallons each=1,025,200 gallons per day.

The following link includes flow rates for reef environments:

http://www.reefland.com/rho/2006/03/water_movement_reef_aquarium.php

From it:


Typical flow rates from various reef environments, after Sebens, et. al. (1997, 1998)
Reef Area Typical Flow speed
Reef crest, fast currents, wave surge 7 - 34 cm/sec, up to 1m/sec
Lagoon 1 - 16 cm/sec
Deep fore-reef (deeper than 25 m) <5 cm/sec
Mid- to deep fore-reef 5 â€"œ 7 cm/sec, or less
Shallow fore-reef 9 â€"œ 16 cm/sec

5cm(2inches per sec )
does not appear to be a bad average assumption for the million gallon per day rhetoric in my opinion.

 

[tmz]

Cap'n Cully. As far as I know, upper reef waters are generally nutrient poor(near zero nitrate and phosphate in the .05ppm range or less) but they are constant with replenishment to those levels ongoing. Going down about 30 to 60 ft nutrient levels incresase 5 to 10 fold. Lagoons with turbid water could be higher. Sodifferent invertebrates will have different needs ,making it hard to manage a mixed reef.

I don't know about you but it's easy for me to exceed those levels in my tanks but very hard to match them on the low end.

 

[Capt_Cully]

<a href=showthread.php?s=&postid=14242721#post14242721 target=_blank>Originally posted</a> by tmz
Cap'n Cully. As far as I know, upper reef waters are generally nutrient poor(near zero nitrate and phosphate in the .05ppm range or less) but they are constant with replenishment to those levels ongoing. Going down about 30 to 60 ft nutrient levels incresase 5 to 10 fold. Lagoons with turbid water could be higher. Sodifferent invertebrates will have different needs ,making it hard to manage a mixed reef.

I don't know about you but it's easy for me to exceed those levels in my tanks but very hard to match them on the low end.

Tom, I was more refering to shallow/lagoon reefs, vs outer wall reefs with many different depths. My point was that siltier/murkier waters in shallow reef zones have more particulate matter in them. A random, non filtered sample might have more disolved or even microscopic solid matter in it. This would, technically, increase the SG of that fluid.

Now, in reality, I've no idea as to whether or not this is actually occuring on a measurable level (certainly not by a run-o-the mill swing arm hydrometer

That was merely the point I was looking to have answered. I wasn't disputing in any way, just curious.

Your response brings up the sometimes forgotten point that there are MANY different reef zones, each with vastly differing ecology.

 

[smatter]

I always go back to my old Tropic Marin glass hydrometer, it's always spot on, no calibration needed, just a rinse in RODI after use. I think I have three refractos lying around.

 

[LauraDlite]

Where can i get the glass hydrometer mentioned above?

 

[plyr58]

<a href=showthread.php?s=&postid=14250086#post14250086 target=_blank>Originally posted</a> by LauraDlite
Where can i get the glass hydrometer mentioned above?

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