Maybe this topic is hidden deep in another discussion thread....but in case not...
I am wondering what different types of containers people use for fish tanks & plant beds. I was going to build a frame and line it with a pool liner. My uncle is a pool man and I thought I could get a scrap piece of liner. Thank goodness my uncle is very knowledgeable man because he told me that even a new liner would be deadly to fish. Just thought I would share that knowledge for anybody else who had the same idea.
Since some of the talk has veered off to heating, I thought I would toss out what Cosmo and I just got. Some background first - we were going to go solar. We looked at panels (but was warned of particulate clogging); then a hose in a solar collector (after doing the math, the water volume heated was low; 100' of 1" line was around 8 gallons. Plus it got costly with lumber, gas, pump.. well over $100.Then the temp rise would only be 5-10 degrees.). We looked at a water-tank based solar collector heater and that was better but needed a diverter at night and cloudy or rain days would be a issue.
Then I looked at stock tank de-icers. Looked perfect except the built-in, nonadjustable thermostat was set for a 35-44 degree range. Too cold. I even looked at spa heaters but cost was higher and it required fancy electrical work. I'm not sure enough of my skills to play with that around water.
So finally I hit on an over the side stock tank heater. Fully adjustable thermostat from 34-90 degrees. Cost was $115 shipped, which seemed costly until looking at the price of building the other systems. We could set it for the temp we wanted. There were two downsides - 1) it's a 1500-watt heater. But I'm not going to run it at higher than 65 and will insulate the outside of the tank, float a styrofoam lid atop it. So heat loss will be reduced. 2) it cannot be in contact with plastic due to melting. I plan to put it inside a metal or clay container that water can circulate through but will keep the heating element away from my liner.
Here is what we got and a link to the cheapest source I found (from Colorado):
What is the metal element made out of? (remember metal and fish water should cause caution.)
And as to floating a foam lid on the fish tank, you might think about simply placing it over and leaving an air gap so as not to reduce the dissolved oxygen too much though I know the oxygen levels are not as much of an issue overnight.
Can't speak for Cosmo, but I plan to isolate the coils and essentially create a water bath. I will use the heater to heat up a barrel of water that will then heat the pond conductively.
I will likely use a 55 gallon barrel in the center of my pond. Since the water inside the barrel will be isolated, I don't care what was inside it (within reason). The pond water will only contact the exterior and I can sleeve that with a couple layers of large plastic bags.
Heater came today.. it's a stainless steel heating element. so metal interaction is not a concern. Now I'm trying to decide if I even need to bother with a water bath or just mount the unit straight into the tank (just insuring it doesn't touch the liner.)