Often it is beneficial to know the water temperature at various depths in your pond. A few reasons to know these temperatures will allow you to:
1. find a thermocline, (cooler water layer)
2. determine if your pond needs an aerator due to formation of thermal layers that do not mix in summer,
3. determine how well your aerator is mixing or turning over the pond, (top to bottom temps will be more uniform the better the mixing); remote areas may not be getting well mixed.
4. determine if you can run your aerator less time and still have adequate water mixing each day,
5. locate deeper areas where spring water might be flowing into the pond,
6. measure deeper water temperatues during winter or ice cover to see if there is any supercooling (below 39F).
7. detect any warmer water zones near bottom in winter
8. find the preferred temperature of fish in deeper water
Sub-surface water temperatures can be measured with relatively low cost electronic temperature sensors that have a probe attached with a wire to the battery powered hand held unit. Now until March 31 2008, Cabelas has the following Minn Kota temperature sensor on 50% off sale for $9.99 (orig price 19.99). If you have one of these units you may want to buy a second one as back-up, replacement, or a gift. I think these discounted units are close-outs and are being replaced by a newer $20.00 version that can be seen in this link. http://www.cabelas.com/cabelas/en/templa...requestid=57747
Sale priced unit below has a 20 ft probe cable and operates with a AAA 1.5 Volt battery. Sale in Cabelas Sale Catalog ends on March 31,2008. Sale items have limited supply. If you want to order, Sale Catalog ITEM NUMBER IS: NJ-01-3663. Catalog code number is NJ-160A. Cabelas toll free phone is 1-800-237-4444.
In the photo I have a copy of the catalog ad plus my Temp Sensor that I've had several years. I attached a lead weight to the probe end to quickly make the probe sink. I marked the sensor's wire with colored tape to identify specific depth increments. I use a piece of foam as a base to hold the unit and to wrap-up the wire to keep it more organized.