Ponds are a significant investment. Building a pond, even a relatively small one, can cost tens of thousands of dollars, and stocking it with fish is not cheap either. If you fertilize, you can easily spend $300 or more per acre each year. Feeding fish, liming, treating weeds—these are all large expenditures and require quite a lot of time and effort—and I have not even mentioned amenities like piers, ramps, or boat houses. Yes, we put a lot of money into our private fishing paradises. However, there are basic investments that pond owners often overlook, even though they are inexpensive and can be invaluable tools for managing ponds. In this installment of Empirically Speaking, I offer my top four tools most likely to be missing from your pond management arsenal.

            The first is a Secchi disk. This is a simple yet useful tool for measuring how deep you can see into the water. Named for its creator, Angelo Secchi, the tool is simply a weighted circular disk painted with alternating white and black quadrants. The disk is usually about 8 inches in diameter and is either mounted on a pole or tied to a rope so that it can be lowered into the water. The average between the depths at which it disappears when descending and reappears when ascending gives the measure for water transparency.

            A Secchi disk is a great tool for determining when to fertilize. You can buy a cheap student Secchi disk for as little as $20 or you can make one for next to nothing. Either way, I recommend attaching it to a 1-inch wooden dowel that is 3 feet long and using a permanent marker to mark the dowel at 12 inches, 18 inches, and 24 inches from the disk (Figure 1). If you can see less than 12 inches, your bloom is too dense and you need to stop fertilizing and keep an eye out for signs of low oxygen. The target water transparency is about 18 inches, and if you can see more than 24 inches into the pond, it is time to add more fertilizer.  

            Next, no pond toolkit is complete without an alkalinity test kit. Alkalinity is a measure of dissolved minerals in the pond’s water. Contrary to popular belief, fish do not like pure water. If you have ever accidentally placed your pet fish in a bowl of pure distilled water, you know what I mean! This is because fish have salts and other compounds intheir blood. If their external environment is too different from their internal environment, they have to fight continuously to keep the salts from diffusing out and the water from entering and swelling their cells. In addition, alkalinity serves to buffer pH, preventing wide swings in pH that are harmful to fish, and it also controls nutrient availability. 

            It is a good idea to test alkalinity annually to see if management actions, like adding crushed agricultural limestone to improve water chemistry, are required. Sure, you can send a water or soil sample away to be tested, but you can avoid this extra step. You can easily test your own water as often as you like with an inexpensive test kit. There are several options, including test strips that you dip in the water and compare the resulting color to a chart ($20), but I prefer the more accurate titration kits. I recommend the test kit made by LaMotte ($50). I personally find that it is the easiest to use and interpret. It allows up to 50 tests per kit, and you can buy refill packs for about $25.  

The third tool that I highly recommend is a good quality seine net. Did you know that simply pulling a seine in shallow areas of your pond in June can tell you almost everything you need to know about the predator-prey balance? You want to see tiny young bluegill and fingerling young bass, and some medium size bluegill, indicating that both predator and prey are reproducing well and bream are surviving. This suggests good balance in the pond. If you see only medium size bream and no young bass, your bass population may be depleted and not reproducing well. Conversely, many tiny bream, few medium size bream, and no juvenile bass suggest you may have a bass-crowding issue.

You can buy a cheap minnow seine ($20) from your local sporting goods store and it will work just fine. If you want a better sample with fewer hauls, a good choice is a custom-built bag seine. I recommend a seine that is 5 feet tall and 30 feet long, with a bag sown in the center that is 3 feet deep. Mesh size should be no larger than ¼ inch. Buoyed float lines and weighted lead lines are necessary. A custom net of this type may run $300, but will last a long time if properly cared for; for a little extra you can have the net dipped in a protective treatment that will extend its life. You can contact a custom net maker to order.

The fourth item seems obvious, yet it always surprises me when pondmeisters don’t have it—a good system to keep track of catch and harvest. I suggest a waterproof paper logbook ($10). Keep it at the pond and instruct everyone who fishes the pond to record species, sizes, and outcome (did you keep it or release it) for every fish caught. Although actual measured length provides more information, it takes a lot of time to measure each fish you catch. Instead, fish size can be recorded in size categories. Size categories for bass might include <13 inches, 13-16 inches, and >16 inches, but this can vary depending on your management objectives. Bluegill categories might just be <6 inches and >6 inches. Make sure anglers record if the fish was released or harvested. For other species, such as catfish, simply recording the catch and release/harvest would be sufficient.

The logbook will provide valuable data at the end of each year. You can tell the status of the fishery, annual trends in catch rate, and if your management activities are leading to more big fish. You will also be able to count the number of harvested fish to see if you are reaching your harvest objectives. You can place a mailbox near the pond to store the logbook for easy access. If you want more and better data, you can also supply a measuring board and ask all anglers to measure each fish accurately. This will allow you to make length frequency graphs so that you can better understand your populations.

            These four tools collectively could cost less than a good steak dinner, yet are often missing from the pond owner’s tool kit. The Secchi disk improves fertilization programs by timing fertilizer application to only when needed, potentially saving hundreds of dollars per year. Alkalinity testing can prevent winter fish kills and ineffective fertilization. A seine can identify issues with predator-prey balance in time to make adjustments to summer harvest. Finally, a good logbook is a running history of the pond, allowing identification of trends and calculation of annual harvest. These four tools can provide the pond owner a greater level of autonomy in the management of their pond, and will allow faster identification of issues as they arise. How many do you have in your toolbox?