When cooling down a fish tank

so i just checked my ice, it was already melted, so i went with an extra large size ziplock bag and filled almost full with ice. I noticed that the temp was starting to go down a little bit, and i don't think the water bottles will go freeze any time soon

 

Oh 20G. ya Big bags will do the trick. Just keep switching them out when they melt. you might want to get those water bottles in the freezer for tomorrow

 

yea, i think the water bottles will take about 24hrs to freeze

 

try adding salt to the ice but make sure you have a good seal on the zip lock bag to prevent the salt from entering into the tank.

What happens is the salt lowers the freezing point of the ice that allows the water to pull more energy out of the ice

 

Salt will speed up the ice melting process, which is not something you want when cooling something down. The salt lowers the melting point of the ice, which is why salt is used to thaw down frozen roads. You want the water to draw out the cooling of the ice, which will attempt to bring the system into equilibrium, not anything else. If we had our way, the ice would never melt so it could keep cooling our tanks.

 

When ice melts, it absorbs heat energy from its surroundings. When you add salt to ice, the rapid melting of the ice can cool the ice and water to below 0 °C. Before refrigeration was invented, ice and salt was used to produce the rapid cooling needed to make ice cream.

 

Ice either in bottles or bags, is an extremely inefficient way to cool a tank. An $8 Wal Mart clip on fan will do wonders in comparison. The fan should easily lower the temp 5-7 degrees in a 24 hr period by evaporation. You will have to top off more often but it works well.

Do the math and you see the BTUs required to lower one gallon of water one degree is tremendous. Ice is definitely not the way to go. Get a small clip on fan and forget about it.