Why don't we use under-gravel heaters for deep sand beds???

[L.Foley]

As I was installing a new freshwater planted tank, I was wondering why don't we use/try to use, under gravel heaters for our deep sand beds in reef aquariums?
Wouldn't this provide better circulation throughout the sand bed, and possibly stimulate better "life" in our sand beds?

Just a thought,
Leland Foley
Mainstream Aquatics

 

[Bill2]

Prolly would create a heat dead zone. I'm sure it has to be super hot near the element to heat the whole tank.

 

[L.Foley]

Bill,
Good point, but to remedy that there are kits from Germany that are basically airline hose that wraps around your existing in-tank heater, and down through your substrate, that you pump water through. The warm water heats the substrate, and exits the tube at the other end of the tank above the substrate. This would keep the tank warm, and prevent the substrate from getting too hot. The potential problem I see is that I rarely have to use my heaters, or in other words, they rarely come on, due other heat sources in/on the tank. So not too much heat would really get to the substrate, since the heaters are rarely on.

Leland Foley
Mainstream Aquatics

 

[L.Foley]

Bill,
Now while thinking I wonder if heating the substrate would cause a negative effect to the fauna in the sand. What made me think, was if you have ever been scuba diving or snokelling, and stuck your hands down into the sand on the ocean floor, it feels dramatically cooler. This may be due to the heat of the sun hitting the first inch or so of sand, but it is easy to feel a big change in temperature.

Leland Foley
Mainstream Aquatics

 

[randy holmes-farley]

It feels dramatically cooler? Huh, I wouldn't have guessed that unless the water is changing a lot in temp during the day, and you dive during the warm parts. I'd be surprised in anything in water can be appreciably warmer than the water just because the sun is shining on it.

As to the heaters, I just don't know. Maybe so many people use sumps that there isn't the drive for undergravel heating. I'm also afraid that it would need to be too hot to keep my tank warm in the winter. I use hundreds of watts, and if the bottom of the gravel were getting hundreds of watts, I'd think it would get pretty warm before it transferred much heat to the tank.

 

[L.Foley]

Randy,
I think the substrate would get warm also, but wouldn't induction currents create upward currents that would prevent the substrate from getting too hot?
In our fresh water planted tanks, we use a 3-4 inch sand bed, that is of a #1 sized sand, and the plants grow great. In fact they won't do well if we don't use a undergravel heater. Tepoot's book explains this and says the entire sand bed will become anaerobic if undergravel heaters are not used. The induction currents keep the lower sand slightly anaerobic, and the upper 2 inches aerobic, thus keeping the plant's roots from rotting as well, and suppling iron to them from the laterite in the bottom of the sand bed.

Leland Foley
Mainstream Aquatics