A benefit of having gravel on the bottom of your pond is firstly that your pond will look more natural. There aren’t any natural ponds out there with pond liners. If you have a gravel bottom pond you can also ensure that the liner material is hidden beneath the gravel. The gravel and rocks also give your pond plants a place to easily grow and attach their roots.
Unfortunately when you have a rock or gravel bottom pond it does provide a good place for pond sludge to develop. When you have this buildup it can be harder to use a skim net or pond vacuum to remove it when you have a gravel bottom. However you can use product such as Microbe-Lift SA (Sludge-Away). Microbe-Lift SA (Sludge-Away) speeds the biological removal of slow-to-degrade organic waste matter from aquatic pond bottoms. This organic matter can become toxic to fish and plant life. As organic solids accumulate on the pond bottom, they begin to break down releasing toxic gasses to the surrounding environment. These gaseous by-products endanger fish, marine life and plants. Microbe-Lift SA (Sludge-Away) removes bottom organic sludge eliminating the potential harmful gaseous compounds. It also helps clarify your pond water at the same time.
The pond bottom of your pond will also have less oxygen than the upper layers of the pond. This is especially if you have stone or gravel in the bottom of your pond. Organic material gets trapped in the gravel or rocks at the bottom of your pond. Often water does not circulate very well at the bottom of your pond. Organic matter is processed anaerobically because our pond water is therefore deficient in dissolved oxygen. This creates the sludge build up that all pond owners want to avoid. If you have a pond it is certainly always beneficial to have an air pump to circulate oxygen but especially if you have a gravel or rock bottomed pond.
Obviously there are disadvantages to a rock or gravel bottomed pond in addition to the above filling your pond with rocks adds cost and colorful pond fish don’t stand out as well as they do in a black-bottom pond. However if you already have a pond with this bottom or you prefer the aesthetics of gravel on the bottom of your pond you can use products to ensure that you minimize some of the downsides. Consider using an additive such as Microbe-Lift SA (Sludge-Away) and have an air pump to ensure that you have a healthy and attractive pond.