Hydroponics FAQ

Welcome to the BGHydro Official Hydroponics FAQ section. Use the links or search box below to find your way around.

What is the difference between HPS and MH and fluorescent lights?

See What kind of lighting do I need to grow plants?

What kind of lighting do I need to grow plants?

There are two primary types of lighting used to grow plants. High Intensity Discharge (HID) is by far the most common, and includes Metal Halide (MH), which is used primarily for the vegetative stage of growth, and High Pressure Sodium (HPS), which is used during the flowering or fruiting stage. You can find more information on HID lighting further down in this FAQ section.

Another popular type of plant lighting is Fluorescent lighting. Fluorescent lighting is used primarily for starting seedlings and cuttings, but T-5 fluorescent bulbs are strong enough to grow short plants from start to finish. It is important to note that not all fluorescent lighting is the same and only certain types should be used for growing plants. Most (if not all) standard fluorescent tubes are fine for illuminating a garage or office, but usually lack the spectrum and intensity needed to sustain plant growth. It should also be noted that if you are growing houseplants that require very little light to sustain growth, you can probably get away with some of the inferior types of fluorescent lights. But, if you are growing plants that need plenty of natural sunlight in order to thrive (such as vegetables and flowers), you will be extremely unhappy with the results you get from these bulbs.

There are three types of fluorescent bulbs that are considered suitable for plant growth: Standard tubes with enhanced spectrum (such as the Verilux), Compact fluorescents and T-5 fluorescents.

Verilux bulbs look similar to the bulbs you typically find in shop lights and offices. The main difference is that, unlike standard tubes which lose their intensity and spectrum in as little as 6 weeks, Verilux tubes retain their properties much, much longer. They also have a spectrum that is extremely close to natural sunlight. They can be used in any standard shop light fixture. They should only be used for growing houseplants, orchids, or for starting seedlings or cuttings.

Compact Fluorescents
These bulbs are available in a variety of wattages ranging from 95W up to 200W. They produce a higher lumen output than regular fluorescents, and are available in 6500K (daylight) for vegetative growth and 3000K (red) to enhance flowering. Unlike regular fluorescents, compact fluorescents do not require a fixture, since the ballast is built in to the base of the bulb. They require a socket (the same type of socket you would use for an HID bulb) and a power cord, and can be used with or without a reflector. Using a reflector, however, will direct more of the light down onto the plants. Another common use for compact fluorescents is to hang them vertically, usually without a reflector, in between large plants to provide supplemental side lighting. Compact Fluorescents can be used for growing houseplants, orchids, or for starting seedlings or cuttings. For plants that do not require full sunlight, or for varieties that tend not to stretch under weaker light, these bulbs can be used for the entire vegetative stage, and in some cases flowering as well.

T-5 Systems
T-5s are the best fluorescent light bulbs available. They are similar to standard fluorescent tubes, only much smaller in diameter. They put out far more light then standard fluorescents, and have a much better spectrum as well. T-5s must be used in a T-5 fixture; they will not work with standard fixtures. They are available in different sizes and configurations, ranging from 2 two bulb fixtures up to 4 eight bulb fixtures. The eight bulb fixture is approximately equivalent to a 600W HPS lighting system. T-5 bulbs are available in 6500K (daylight) for vegetative growth and 3000K (red) to enhance flowering. T-5 systems are excellent for starting seedlings and cuttings, and in many cases take plants from start to finish, provided you keep the plants on the short side.

What size (wattage) lighting system do I need?

There are two things to consider when deciding what size lighting system to use: the actual area in which the plants will be taking up, and how tall you want your plants to grow. 150-175 watt lights are primarily used for seedlings or cuttings, though they can be used for growing plants to maturity if the plants are kept short. 250 watt systems are good for areas up to 2.5' square at the most, as long as the plants don't get taller than about 2'. 400 watt systems cover a primary area of about 3' x 3', or up to 4' x 4' max. 600 watt systems cover a primary area of about 4' x 4', or up to 5' x 5' max. 1000 watt systems cover from 4' x 6' up to 5' x 7'. The taller you plan to grow your plants, the higher the wattage needed. This is because the light intensity diminishes by 50% for every foot you move away from the bulb. So, if your plants reach 4' tall, then the leaves at the bottom of the plant are receiving only around 12% of the light that the top of the plant is getting!

What are the main differences between the different brands of lighting systems that BGH carries?

At the time of this writing, BGH is the only company that offers growers the ability to choose the reflector you want with the ballast you want and the bulb that you want. This enables growers to choose from literally hundreds of different lighting configurations to ensure that you are getting exactly what you want, without paying for something you didn't want (if only someone had offered this when we were first starting out as growers...!).

BGH carries the following brands of lighting: Sunlight Supply, P.L. Light Systems, Hydrofarm, EuroSystems, Gavita, and of course, BGH We have carried many other brands over the years, but found that the mix we now offer gives you, the grower, the most number of choices between economy and performance, regardless of your lighting budget. We carry only name brand lighting systems because of the fact that most, if not all store-made or "no-name" systems lack the proper U.L. and/or C.S.A. approvals, meaning that they have not gone through the extensive and extremely expensive testing process necessary to ensure that they are completely safe for you to use at home or in the greenhouse. It's just not worth taking the risk that you might return home one day and be greeted by the fire department because someone sold you an inferior lighting system! (In case you're wondering, BGH lighting systems are manufactured for us by one of the largest manufacturers/distributors of aquarium lighting in the U.S. and are U.L. approved - we don't like to take chances either!).

The main differences between the various brands of lighting systems are found in the reflectors and the ballasts, so rather than talking about the different brands, let's instead talk about the differences in the components that make up these systems.


BGH offers the following brands of ballasts: Sunlight Supply, P.L. Light Systems, EuroSystems and BGH We now also carry digital ballasts.

Sunlight Supply is the leading manufacturer of horticultural lighting systems in the U.S. We are offering their five most popular ballasts:

Sun System X (EconoGro) - The EconoGro Ballast is Sunlight's economy priced ballast, which they import from China. Although they do not manufacture the ballast themselves, they were so impressed by the overall quality, fit and finish of the product, not to mention the incredibly low price, they realized that growers on a budget would appreciate having it as an option. Features include: die cast aluminum ballast housing, louvers for cooling, rubber feet, multi volt ballast, 8 foot grounded power cord, 15 foot detachable lamp cord and a white powder coated finish. They are now covered by a 5 year warranty and are available in the following wattages: MH400, MH1000, HPS400, HPS 600 and HPS 1000.

Sun System I - This is Sunlight Supply's highest quality ballast. Sun System I ballasts include aluminum heat sync ballast enclosure, heavy-duty key-way handle (in case you want to mount or hang them), Advance or Magnetek brand multi-volt transformer, 8 foot grounded power cord, 15 foot detachable lamp cord, rubber feet, high temperature capacitor (if applicable), on/off switch and technical guide. They are covered by a full 5 year warranty and are available in just about every wattage imaginable. All systems are UL, CUL and CSA listed. Changing the SSI ballast from 240V to 120V has now been made easier. Simply unplug the 120V MVP power cord from the ballast and plug in the 240V MVP power cord and you're set. The MVP power cord only makes connections with the appropriate voltage of the power cord you select so there's no rewiring or switches to flip.

Sun System X (EconoSwitch) - The SSX EconoSwitch has all the features of the SSX, but adds the ability to run either MH or HPS lamps from one ballast. Just flip the exterior mounted switch to either MH or HPS, screw in the appropriate bulb to your reflector, and you're set. It is available in 400W and 1000W versions.

Sun System VI (Switchable) - This unique ballast has all of the high-quality features that are incorporated into SSI fixture, but adds the ability to run either MH or HPS lamps from one ballast. Just flip the exterior mounted switch to either MH or HPS, screw in the appropriate bulb to your reflector, and you're set.

BGH also carries the Sun System VII (Combination Ballast) - The Sun System VII Ballast is actually two ballasts in one. It has all of the features that are incorporated into the SSI fixture, but adds the ability to run both an MH and an HPS lamp at the same time from one ballast. Like the SSI, the SSVI is Sunlight Supplys highest quality ballast. It is available in an 800W model (400W MH + 400W HPS) and a 1000W model (600W HPS + 400W MH).

In addition to Sunlight Supply, BGH also carries its own brand of ballast, as well as P.L. Lighting Systems and EuroSystems.

The BGH Ballast assemblies all feature quick-disconnect adapters and multi-tap transformers, which means that you can switch them from 110/120V to 208V, 220/240V or 277V in just minutes! The 15' heavy duty detachable lamp cord (included) makes installation a snap (no ''hard wiring'' like many other systems). Our ballasts are made by one of the largest manufacturers/distributors of aquarium lighting in the U.S. They feature white powder coated sheet metal housing with LOTS of louvers on three sides for exceptional cooling. VERY quiet and extremely reliable with a proven track record over 12 years long! The BGH ballast is made in the U.S. and comes with a full 5-year warranty.

The P.L. Lighting Systems ballasts also feature multi-tap transformers and detachable lamp cords. They are very similar to the BGH ballasts in terms of quality, with the addition of a key-way handle that makes them very easy to mount to the wall. When purchasing a complete lighting system, P.L. ballasts are options that are only available with P.L. reflectors; they are not available with any other complete lighting system package. You can also purchase P.L. ballasts by themselves.

EuroSystems ballasts are high quality ballasts that are made in Europe. The most exciting ballast that EuroSystems offers is the Twin 600W Ballast, which is able to operate two 600W lights from one ballast. You can read more about EuroSystems in the EuroSystems category on our website.

The Digital Ballast represents a breakthrough in HID lighting, and offer many benefits:

Works with both MH and HPS bulbs
Energy savings of up to 30%*
Produces no heat
No start-up spike of electricity
Power factor (efficiency rating) is 99%
Consistent wattage output - improves bulb life
Components are American-made
No stroboscopic (flickering) effect - as close to natural sunlight as you can get
These ballasts also have a built-in safety feature. If an open circuit exists while trying to ignite the lamp, the ballast will stop and then attempt to ignite the lamp again every 30 seconds for 2 minutes. The ballast will then go into a sleep mode for 30 minutes and then repeat. This saves many dangerous and unnecessary attempts to ignite and burn out the ballast, which could result in safety hazards.


The reflector is undoubtedly the single most important factor to consider when choosing a lighting system. The reflector dictates whether the light is concentrated on the plants, or splashed up against the walls. While some bulbs are a little brighter than others, a quality reflector can reflect up to 50% more light straight down onto the plants than a lower quality reflector. Heres a common mistake that first-time growers make. They see a reflector that is advertised as covering up to an 8 x 8 area (with a 1000W bulb installed). Then they see another reflector advertised as covering only a 4 x 6 area, and for more money, too! Which would you choose? Well, consider this: Lets say that a 1000W HPS bulb puts out 140,000 lumens (lumens is a measure of light intensity). Now, lets say that you have a jar containing 140,000 marbles, each marble representing one lumen. You pour this jar into an area that measures 8 x 8. You get a pretty thin layer of marbles. Now, pour this same jar into a 4 x 6 area, and you have a much thicker layer of marbles, right? Is it starting to make sense? Stay away from the reflectors that throw the light all over the place, unless you are growing houseplants! The smaller the area covered, the brighter it will be, and the better your plants will grow and yield. Horizontal hoods are the best choice for plants that require a lot of light, such as most vegetables & flowers. Horizontal hoods direct the light straight down on the plants, throwing more intense light over a smaller area. This is by far the most popular choice among growers. Air-cooled hoods have flanges that allow you to hook an exhaust fan to the hood to suck out the hot air generated by the bulb, thus reducing the amount of heat in the grow room.

BGH offers the largest selection of reflectors anywhere, by leading manufacturers such as P.L. Light Systems, Sunlight Supply, Hydrofarm, and, last but not least, BGH.

You can find detailed information on all of the reflectors we currently carry in the Reflectors category on our website.

How often do I need to replace my bulbs?

BGH recommends that HPS bulbs should be replaced at least every 12 months (8 months or less is ideal). MH bulbs should be replaced every 9 months (6 months or less is ideal) for maximum efficiency. The use of a light meter would be the best and most accurate way in which to measure your bulbs output as well as to help with bulb replacement timing.

What is the difference between an MH Regular and Super Bulb and how do I know which one I need to buy?

A Metal Halide Super Bulb has a higher lumen (light) output, and is almost always position oriented. These bulbs have a pin sticking out of the side of the mogul (base) where the bulb screws into the socket. These bulbs require a position oriented socked that is designed to catch the pin so that the bulb is rotated into the correct position, otherwise the bulb will not perform as expected. In addition, these Super MH bulbs must be burned in a horizontal position only. All other bulbs (non-position oriented), including the MH Regular bulb, can be burned in either a horizontal or vertical position (i.e. they are universal) unless otherwise noted in the individual bulb description.

What is a recommend lighting schedule for Vegetation and Flowering?

For Clones/Seedlings and Vegetative Growth BGH recommends using an 18 hours on/6 hours off lighting schedule. In order to induce your plants to flower we recommend subjecting your plants to a 12 hours on/12 hours off lighting schedule.

Is it OK to leave my lights on 24 hours per day?

BGH does not recommend running lights 24 hours under any circumstances. Your plants need a time to rest and grow. This is achieved during the dark period. Running your lights for 24 hour cycles may have a detrimental affect on your lighting system and your plants, not allowing them to develop properly. In addition, many plant species do most of their feeding during the night, especially when daytime temperatures are high or humidity levels are low.

How do I determine how much my electric bill will increase by using a lighting system?

First, find out what your electricity provider is charging you per kilowatt hour (KWH). In Los Angeles, its approximately $0.10/KWH, but this number will vary from city to city. This number represents what a 1000W lighting system will cost you per hour to run. So, if you have a 400W system, the number to use in the following steps would be .04, for a 600W system it would be .06, and so on. Next, multiply this number by the number of hours per day you plan to operate your lighting system. This will give you the cost per day. Finally, multiply this number by 30 to see approximately what it will cost per month.

Refer to the following example:
0.10 (KWH cost for a 1000W lighting system) x 12 (hours per day) x 30 (days per month) = $36.00 per month

Click here for more information on electricity cost, as well as a handy Power Estimation Guide

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