This is a note by Tony Griffitts that will be helpful for those who want to know about lighting types for freshwater aquarium and what things that needs to be considered when selecting a new lighting system for your freshwater aquarium plants.There has been a revolution in aquarium lighting in the last couple of decades that the marine side of the aquarium hobby has been quick to embrace, but the freshwater side appears to be lagging behind. Perhaps it is because of the misunderstanding, misconception, or just plain old bad information floating around on the freshwater side of the hobby that is making it slow to embrace modern aquarium lighting systems.
The aftermarket of aquarium lighting systems that reef hobbyist have embraced for years have proved to be very beneficial for coral and marine fish. These lighting systems can also provide the same health benefits for freshwater aquariums. These bright modern lighting systems can be found in many types and configurations. The most common aftermarket lighting systems today are Compact Fluorescent, T5 High Output (T5 HO) Fluorescent, HQI Metal Halide (double ended), HID Metal Halide (socketed end), and LED (Light Emitting Diode).
Bright light over a freshwater has health benefits for the inhabitants. Bright light stimulate plants and algae to take up harmful nutrients and produce oxygen. Ammonium and Nitrate are well know plant fertilizers that are constantly being produced in the aquarium. A bright light over a well planted aquarium will help take up the nutrients as they are being created. The benefit is very little to no Nitrate accumulation in the tank. Since Nitrate will lower the pH as it accumulates in the system, a brightly lit aquarium will normally have a much more stable pH. Excessive amounts of Nitrate are linked to Hole in the Head disease (HITH) in large freshwater cichlids and Head and Lateral Line Disease (HLLE) in many marine fish.Keeping Nitrate under control is very important in maintaining a healthy aquarium eco-system. If you have any Nitrate accumulation in the system over the course of a month or two, your tank is out of balance. Most freshwater aquarium plants hobbyist do a regular water change on their tank (that helps reduce the amount of Nitrate that is accumulating) without understating the reason why they are necessary. The number one health benefit from water changes is the reduction of Nitrate on a system that is out of balance. Adding a bright light over a tank with fast growing aquatic plants can have a significant impact on reducing Nitrate accumulation in the aquarium.
For freshwater hobbyist with large cichlids such as Oscars that like to redecorate, and fish that like to eat plants, keeping plants in a brightly lit aquarium would not be practical, but you can still achieve the benefit by circulating the water through a refugium. Refugiums are very popular in the reef side of the hobby. A refugium is a separate tank with a bright light that is set up with algae (in the case of the reef hobby) or with fast growing plants (in the case of the freshwater hobby). Refugiums are set up much like a trickle filter (a.k.a. Wet/Dry filter) normally located underneath the main display tank.Water is brought to the refugium by either a hang on the back overflow system or by a built in overflow system in the aquarium. A small sump pump is placed in the refugium to return water to the main display. You do not need to cycle water very quickly through the refugium to achieve the benefit of Natural Nitrate Reduction (NNR). The refugium can also be used to house freshwater shrimp that help control algae, or other small freshwater fish that would be eaten if they were placed in the main display.
Freshwater aquarium hobbyists often worry about adding bright light over their aquarium will cause an excessive algae outbreak. Algae is a natural part of the aquarium. Excessive algae growth is not caused by bright light; it is caused by excessive nutrients. Algae growth will often be excessive in the beginning, until the plants have established themselves, and then start out competing the algae for nutrients. It is always best to start off with fast growing plants or add fast growing plants when the aquarium has an algae problem.Indeed, Green water algae bloom will sometimes occur on aquariums with bright lighting systems. In some cases the algae bloom may go away on it’s own after a month, but in some cases, the nutrients the algae may be thriving on may be coming from your tap water. The addition of a small Ultraviolet Sterilizer to the filtration system will eliminate any green water. Once the bright light system is well established with plants the algae will no longer be a problem.
Many freshwater aquarists with brightly lit planted tanks will confess that they rarely have to clean algae off the tank walls. This is a fact, when the nutrient level is low, there is very little if any algae growth. In many cases, you may find that the addition of aquatic plant fertilizers may be necessary to keep your plants growing well.
Bright light also helps enrich the color of the fish. Bright light helps darken the pigments of many fish, making them stand out. Discus hobbyist; don't buy into the myth that discus don't like brightly lit tanks. They may need a few days to acclimate to the brighter light, but in time they will settle down, their colors will start to become even brighter, they will grow quicker, they will spawn, and their water quality will improve.
The addition of a CO2 (carbon dioxide) system will speed up the rate at which plants will take up nutrients, and their rate of growth - see Light CO2 and Aquarium Plants. While CO2 systems are not necessary on a brightly lit system, they can help speed up the uptake of nutrients in a system that is out of balance.