View Full Version : What's a Dense Reef Safe Material
hwttdz
02/20/2009, 11:30 PM
I'm looking for a ballast for a DIY project about which I hope to share more once I get a system up and running. At this point in time I am looking for a reef safe material to use as a ballast, for my purposes denser is better. I imagine using lead beads and filling the gaps with sand is not a good call. Right now I'm using crushed coral, will use sand which is a little denser, on the order of 2 g/cm^3. Any other suggestions? Thanks.
xJake
02/20/2009, 11:45 PM
If you could describe what you're trying to do in a bit more detail then I might be able to help. I'm assuming by "ballast" you're referring to some kind of stabilization weight and not a lighting/electrical ballast - which most RC users think of when they read the word "ballast." There are a large number of materials that could possibly be used, but again, it would help to know what you're attempting to design/build.
For now, as a general piece of advice, I would suggest some type of dense metal coated in a plastic epoxy. This would give you the weight/density you need and even just a thin epoxy coating would make it completely reef-safe.
hwttdz
02/21/2009, 12:11 AM
Correct I meant ballast in the provide balance sense, and also possibly sink some volume of air under water.
I'm working on a auto top off system which is controlled by air pressure, and depends on having a body of air trapped inside a container. As the water level in the sump decreases, the air pressure in the bubble decreases, pulling water from a reservoir. Some of the benefits of this system are it's cheap and it can make very fine adjustments in water level (I expect water level to fluctuate by on the order of 1/8"), there is no float valve to fail, it's easy to add to the reservoir (not the case for some air pressure driven systems which require a vacuum to be primed in the reservoir each time).
I haven't really used epoxy much. But I'll look into it.
For some reason this recalls when I worked in a plasma physics lab and we used to build lead enclosures for some of the experiments because they would give off crazy radiation. I remember the first time I picked up a lead brick, wow.
xJake
02/21/2009, 12:23 AM
That sounds similar to a "nurse-style" automatic top-off system, but I'm not really sure how a ballast would fit into such a design...
http://i258.photobucket.com/albums/hh277/jgraving/ReefCentral/top-off1.png
Salamander
02/21/2009, 12:25 AM
How about some Portland cement? Just need to cure it properly.
And you know we all want a diagram of your scheme.... :)
hwttdz
02/21/2009, 01:16 AM
It is similar to the nurce in some ways, in fact I was originally planning on a nurce.
Ok here's an awful picture, which also makes it very unclear why I need a ballast.
http://hwttdz.homelinux.net/img/mypics/system.png
(gotta love ms paint)
So the greenish is the reservoir, the bluish is the sump, the tall column is what I will call the bubble container. Black is tubing. The arrows on the left are a super small water pump pushing water up into the descending pvc, which is what the rigging in the reservoir is. I should probably just find a digital camera and take a picture of the one I have in my kitchen which consists of:
1 inverted pint glass (bubble container)
1 pot (sump)
1 pint glass filled to brim (pvc)
1 casserole dish (reservoir)
Also if you try this out, find food coloring, watching dye flow through tubes is entirely too much fun.
What happens is that as water is removed (by evap) from the sump the pressure in the bubble decreases and it pulls water from the reservoir. Critical to this plan is that the head pressure of the reservoir is constant. Hence the little water pump (aqua lifter type deal) that moves water from the bottom of the reservoir to the downward part of the pvc. This fills up until the top of the tee, at which point it just slides back down the other side of the pvc.
Using this barometer type system one can put the reservoir either above or below the sump. Imagine the reservoir is below the sump, if you increase the height of water in the bubble column, then the water being pulled down by gravity increases the volume of the bubble until the difference in pressure supports the height of the water column. Further decrease of water height in the sump causes the height of the water column to increase which increases the pressure differential with the reservoir to the point where the ambient air pressure is so much higher than the bubble pressure that it is able to overcome the head height and push water uphill.
If the reservoir is above the sump one needs higher than ambient pressure in the bubble (this is where the ballast comes in). In order to do that you need to have a negative height water column in the bubble container. This of course means that the bubble container is displacing more than it's own worth in water, so it wants to float, hence you put some ballast in the bottom to keep it anchored. Here because the air pressure in the bubble is higher than ambient pressure it prevents a siphon from forming. As water drops again bubble pressure decreases allowing water to go downhill.
Plan is to run the aqualifter on a timer, so it's on maybe 2 hours a day, in 4 or 5 different stretches depending on the timer I find.
xJake
02/21/2009, 02:19 AM
<a href=showthread.php?s=&postid=14446395#post14446395 target=_blank>Originally posted</a> by hwttdz
It is similar to the nurce in some ways, in fact I was originally planning on a nurce.
Ok here's an awful picture, which also makes it very unclear why I need a ballast.
http://hwttdz.homelinux.net/img/mypics/system.png
(gotta love ms paint)
So the greenish is the reservoir, the bluish is the sump, the tall column is what I will call the bubble container. Black is tubing. The arrows on the left are a super small water pump pushing water up into the descending pvc, which is what the rigging in the reservoir is. I should probably just find a digital camera and take a picture of the one I have in my kitchen which consists of:
1 inverted pint glass (bubble container)
1 pot (sump)
1 pint glass filled to brim (pvc)
1 casserole dish (reservoir)
Also if you try this out, find food coloring, watching dye flow through tubes is entirely too much fun.
What happens is that as water is removed (by evap) from the sump the pressure in the bubble decreases and it pulls water from the reservoir. Critical to this plan is that the head pressure of the reservoir is constant. Hence the little water pump (aqua lifter type deal) that moves water from the bottom of the reservoir to the downward part of the pvc. This fills up until the top of the tee, at which point it just slides back down the other side of the pvc.
Using this barometer type system one can put the reservoir either above or below the sump. Imagine the reservoir is below the sump, if you increase the height of water in the bubble column, then the water being pulled down by gravity increases the volume of the bubble until the difference in pressure supports the height of the water column. Further decrease of water height in the sump causes the height of the water column to increase which increases the pressure differential with the reservoir to the point where the ambient air pressure is so much higher than the bubble pressure that it is able to overcome the head height and push water uphill.
If the reservoir is above the sump one needs higher than ambient pressure in the bubble (this is where the ballast comes in). In order to do that you need to have a negative height water column in the bubble container. This of course means that the bubble container is displacing more than it's own worth in water, so it wants to float, hence you put some ballast in the bottom to keep it anchored. Here because the air pressure in the bubble is higher than ambient pressure it prevents a siphon from forming. As water drops again bubble pressure decreases allowing water to go downhill.
Plan is to run the aqualifter on a timer, so it's on maybe 2 hours a day, in 4 or 5 different stretches depending on the timer I find.
That's definitely a unique idea, but I don't know how practical it would be. The concept seems very solid though, so I would be interested to see your results. The only flaw I can see is in the aqualifter pump. I've never been able to completely trust a top-off system that relied on any type of pump. I think it would be much more reliable if you could somehow find a workaround to make your design completely gravity reliant (which would probably just lead you back to a variation of the nurce system). Personally, I've never had a float valve fail, so I use them on pretty much every system I work with.
Definitely post some photos though. I'm sure there are plenty who are interested in seeing your concept in action.
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