Lighting The Planted Tank–Frequently Asked Questions
Open AllClose All- 1. Do I have enough light?
- Light is like money. If you have to ask you don't have enough. Seriously though, no standard aquarium fixture comes with a light, that out of the box, is able to actually grow most plants.
- 2. How much light do I need?
- Depends on a lot of factors. Size of the tank and what you want to grow are the too most important factors. For tanks between 20-75 gallons you should have at a minimum of 2 WPG (watts per gallon)?
- 3. What is WPG and how do I figure out my WPG?
- WPG or watts per gallon is a rough rule of thumb that measures how much light you have. To figure your WPG you just take your total watts and divide it by the number of gallons your tank holds. Example: Standard 55 gallon tank normally comes with either 2 18 watt bulbs for a total of 36 watts or a single 40 watt bulb. In the first case 36÷55=0.65 wpg. In the second case 40÷55=0.72 wpg. For a 55 gallon tank you really want around 110 watts. Note that WPG is based on fluorescent watts and US gallons. Also it was based on T12 lighting with basic reflectors. With better lighting technology and reflectors you can get by with less light.
- 4. Will incandescent/halogen lights work?
- No. Some people have had some success with them. But they are much better heaters than lights.
- 5. What is this kelvin or color temp I hear about?
- Kelvin is a measure of the color temperature of light. Click on kelvin for more info. Now that your brain is really hurting just understand that lights in the 5000k to 10000k range work best for plants. 5000k lights will look very yellow to many people and 10000k lights can look a bit blue and harsh to many people. Some of the best bulbs are in the 6500k-8800k range. GE makes a 9325k bulb that is very popular with many people.
- 6. If I have three 3000K bulbs do I have 9000K?
- Nope. Kelvin is not cumulative. If you use 3 3000k bulbs at the same time you have 3000k light.
- 7. Are actinic lights good for plants?
- The jury is still out on this one. Many people feel they don't do all that much for plants. I would not recommend using all actinic lights. But if you have met the basic light requirements you can use an actinic light. There have been some reports that they do cause algae.
- 8. Will good reflectors multiply the amount of light I have?
- Nope. Reflectors are not magic and can't make more light. But good reflectors will get more light into the tank and may allow you to use less light.
- 9. What's the difference between a T12 and a T8 bulb?
- In the case of fluorescent tubes each T is equal to 0.125” or 1/8th of an inch. So a T12 bulb is 1.5” in diameter and a T8 bulb is 1” in diameter.
- 10. What's a PC or CF bulb/light?
- A T5 bulb is a bulb that is 0.625” or 5/8” in diameter. They are becoming very popular as they are a very efficient way to light a tank.
- 11. What's a T5 bulb/light?
- A T5 bulb is a bulb that is 0.625” or 5/8” in diameter. They are becoming very popular as they are a very efficient way to light a tank.
- 12. What's a MH bulb/light?
- A MH bulb is a metal halide bulb. A very high powered lighting source. Very common in the reef hobby but not so common in planted tanks.
- 13. How long should my lights be on?
- Most commonly 8-10 hours. Some people will run them as long as 12 hours.
- 14. If I don't have enough light can I just leave my lights on longer?
- Nope. Won't work. Might even encourage algae.
- 15. I have a 4' long tank. Can I just use a shop light?
- You can use anything you want. But be advised that shop lights are not normally made to work in moist or humid conditions like one finds over an an aquarium. Also shop lights are designed to light up large areas and are not make to direct most of the light straight down. So if you decide to use shop lights just figure them as no more than 60% efficient.
- 16. What is ODNO?
- ODNO stands for Over Driven Normal Output. It's a method of getting more light out of standard fluorescent bulbs than they are rated for. It does work. However it can be a fire or electricial shock hazard. If you want more lights do a Google search for ODNO LIGHTS.