Water Temperature Swings

[hooksbob]

My water temperature swings from 55 at night to 75 during the day on a hot afternoon. I assume the grow beds are the culprit. I live in central California. What can I do to keep my water temperature steady at night, while not causing it to excessively heat during the day. I have not tries simply applying a heater to the appropriate temperature for Tilapia yet.

I currently have goldfish and koi to cycle my system.

[TCLynx]

Is it a flood and drain gravel bed type system?
If so, yes the grow beds flooding and draining make really effective heat exchangers with the air and will do much to bring your water temperature closer to the air temperature.

How do your beds flood and drain? Siphon or timed flood and drain? How big is the system?

There are a couple simple things people sometimes do to deal with temperature swings.

Some people will shut down their pumps at night during the winter to avoid chilling the water so much, of course this means you have no filtration overnight which could be a problem and the first flood in the morning is likely to chill the water a bit unless you wait till it is getting warmer later in the day but again no filtration is happening.

Another option might be to run constant flood during the (undesirable temperature period) Like overnight in the winter or if it gets way too hot in the summer perhaps you want to run constant flood during the afternoons. This is easy to do if you have a timed flood and drain system or bell siphons. With timed flood and drain you might just set your timer to run constantly through the problem time periods and that could be easily changed seasonally. If you have a bell siphon system you just remove the bells and the beds suddenly become constant flood beds. This method doesn't really allow for the automation of the changes and would require you to put the bells back and pull them out if you are wanting to make the shift daily. Loop or other siphons are harder to switch to constant flood. I have changed an indexing valve system to constant flood by pulling the innards out of the valve and then flipping all my stand pipes so the beds would stay flooded and just setting the pump to run constantly.

[davidstcldfl]

You could try shading your media beds to keep them a little cooler during the day. If you can swing the little extra cost...use the alumi-net....it's cooler underneath then conventional shade cloth. Also shade your fish tank and sump, if you have one.
By shading, you'll also keep the algae growth down. If you get much of that growing, then you'll have another issue....less D.O. in your water at night, then during the day.
Just because you add shade, won't stop your water from eventually warming.....like TCLynx said...you have the 'air temperatures' to deal with. It should help with the 'swing' though.

[rfeiller]

florida just does not have a lot of problems that CA has to deal with. temperature swings between night and day of 50 degrees here in san jose, ca is not uncommon. at my place in NM it can easily be 75 degree differential. extremely difficult to maintain any type of even temp.

[urbanfarmer]

You really only have 2 options that don't require adding/wasting energy into your system.

1) Increase the thermal mass available to be heated during the day. This can effectively provide enough residual heat during the night to reduce the temperature swing.

2) Decrease the heat loss. One way to do this is by insulating more surface area. As mentioned above, you can disable areas that may act as efficient heat exchangers with the atmosphere.

Your other 2 options are to add energy in the form of heat into your system.

1) Build (or buy) a solar water heater.
EXAMPLES:
http://www.youtube.com/watch?v=LJcykIg8oHU
http://www.youtube.com/watch?v=MU6I9YU6ihE
http://www.youtube.com/watch?v=GGigjqUW8pQ

2) Add an electric or combustible heater to your system.

[hooksbob]

great feedback. i am trying a small heater, but my concern is hot days will result in 90 degree water; still a 20-25 degree swing. My system is 100 gallons tank, and ~100 gallons grow bed, ebb and flow. I get full sun all day, so maybe some opaques cover for the beds; corrugated fiberglass type?

One of you suggested a fabric shading material for the beds. I could research that also.

[rfeiller]

home depot, osh all carry shade cloth

[TCLynx]

A 100 gallon tank is rather small for an outdoor system without protection. Smallest I feel comfortable with here in Central FL is a 300 gallon tank and I still get big enough temperature swings to have caused me to put up the 40% aluminet shade cloth.

[urbanfarmer]

The thing with micro systems (under 500 gallons or so) is that you have more problems with high variability with everything from pH to temperature. However, this weakness can also be a strength. A small, inexpensive aquarium heater may suffice to keep your system going through cold swings and insulation and shade or any other protective structure can often be made in no time at an insignificant cost. The return on investment is high because of how much enjoyment a hobbyist can get out of their home system. Smaller systems can do things the larger commercial systems cannot afford to do in a cost effective manner. Just learn the basics, and you will be able to manage your system any way you want.

[hooksbob]

I put up shade cloth over the beds, and over the tank today. I also added a heater and will watch the temperature in the am.

I also added 4 air stones.