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Algae Scrubber Basics 7 of 14

Posted 02/19/2012 at 08:32 AM by Floyd R Turbo

Big Basic Change #2 – Alternative High-Intensity Lighting

Around the same time that the screen sizing method was changed, another suggestion was made: you can use twice the wattage of lighting and cut the photoperiod in half. This has a couple of advantages:

The first and primary advantage is the fact that more intense light promotes greener growth faster. This is especially useful in systems that have an initially high nutrient load, or systems that are overrun with algae in the display tank. More intense light will penetrate deeper into the algae mat. In a high nutrient system, the screen tends to grow darker (brown or black). This dark growth prevents the light from reaching the ‘roots’ of the algae, which may lead to the algae detaching from the screen more easily between cleanings. In systems that have a lot of algae in the display tank, it is more difficult to establish a preferred growth location (the Algae Scrubber screen); increasing the light level on the screen can greatly assist in this battle.

The second advantage is increasing lamp life, or more accurately, increasing the time between the need for lamp changes. Since you are only running the lamps half the time, they will last twice as long. This is of course offset by the need for twice as many lamps, but if you combine the new screen sizing guideline together with the higher-light guideline, in most cases you are reducing the overall wattage requirement by half or more versus the old tank-size guideline.

The caveat to this rule is that you must keep an eye on the type of growth. You want green hair algae; anything else requires an adjustment to the ON cycle. If you are getting dark growth, then you need to increase the photoperiod. If you are getting yellow growth, you need to decrease the photoperiod. I suggest making adjustments in 1 or 2 hour increments per week until you get the desired green growth.

Also, as the lamp will eventually start to weaken, you need to pay attention to your growth. Around the 3 month point, the growth may start to get darker. If/when this occurs, you will need to start increasing hours until it grows green again. When you reach 18 hours, it's time for new bulbs. Keeping track of the “on” time that you use will greatly assist you, as you will be able to see a pattern developing. Growth can vary from week to week, but should be relatively consistent on the long term, as long as nothing else changes; changing feeding amount, rearranging the tank, adding more LR, an unknown dead fish, etc, can all affect the color of the growth. Constantly fiddling with the photoperiod should not be necessary after the Algae Scrubber is “dialed in”. You should only need to adjust upward about 1 hour per week as the lamps weaken.

NOTE: Yellow growth is a spongy, gooey type of growth that is also great at light blocking, and is a result of not enough nutrients being delivered to the screen/algae in proportion to the light provided. To resolve this, increase flow if possible, add iron, or reduce the number of hours. You can also increase feeding as long as it’s not enough to overwhelm the Algae Scrubber and cause dark growth.

T5HO Users: This rule has a little bit of a drawback to it for T5HO users. If you are using a stock fixture, this method doesn’t really apply. However, if you are getting yellow rubbery growth, you can back down the photoperiod. However, I would try trimming the screen down first. I did this and the growth got much better. I was running a 20” wide screen and after taking some PAR measurements, I realized that the light in front of the last inch of exposed lamp dropped dramatically, so I just cut that part of the screen off (actually I cut 3” off each side) since I was just getting red turf there anyways and was tired of scrubbing it off. If you are using a DIY T5HO fixture, you might be able to use narrower reflectors and squeeze another lamp in. You lose a little in reflector efficiency, but gain more in additional lamp wattage.

CFLs and Reflectors

The most common CFL used is the 23W Spiral. This is the actual wattage, not the equivalent wattage. There are a few different type of CFL lamps, and each one has a different ideal application. These are: spiral CFL, linear CFL, floodlight CFL.

A bare lamp will work without a reflector, but it will do the job much, much better with one.

Spiral CFL

The spiral CFL is definitely the most common type available and the most widely used. There are 2 ways to orient the lamp: with the end pointing at the screen or with the side facing the screen.

With the end lamp pointing at the screen, a reflector is a must-have piece of equipment. Without a reflector, a lamp pointed directly at the screen will do very little, since a small percentage of the light comes out of the end of the lamp. The cheapest, easiest, and most common reflector for this orientation is the dome-style reflector, which is available just about anywhere.

This reflector provides a wide light signature, since the side light is reflected to the front. They come in several sizes, and you want the biggest reflector you can fit in the space, relative to the size of the screen, that is.

The dome reflector does the job just fine, and one of these should be used at a minimum. However, it is by no means the ‘perfect’ reflector. The reflector has a ribbed, dull surface that does a good job of diffusing the light, but it is not as efficient as a shiny, highly polished spectral reflector. Also, about 1/4 or so of the lamp (depending on the brand) sticks out past the reflector, and most of that light does not get directed toward the screen.

Using several different sized round reflectors can be done also when space is a limiting factor, even though the smaller reflectors are not as effective. This is probably not an issue for very many people anymore due to the new screen sizing guidelines.

With the side of the lamp facing the screen, the reflector is usually a DIY job With a side-style orientation, more light is shed directly to the screen, but you still need to re-direct the light from the sides and back of the lamp towards the screen. There are a few fixtures that you can buy with integral reflectors, but most are very small. Most off-the-shelf light fixtures are for use in a shop or garage and have a half-round solid section, which may or may not have a reflector. If it does not, you can simply line it with aluminum foil or another highly reflective material.

The setup below uses off-the-shelf shop lights. The fixture on the left has reflective material installed.

The advantage to the side-lamp design is that since you can hang the lights from above, they generally take up less space (depending on your reflector) versus the dome reflectors.

In order to spread the light out evenly and wide (but not too wide or you’ll lose intensity at the screen), you want a wide reflector. Finding such a reflector is not easy. Since spiral CFLs can be considered a point source (more of a “blob” source, but this is for simplicity), using an HID reflector can be effective. A DIY beer can reflector can work also. Even some Mylar or aluminum foil will do the job.

Searching for a flexible reflector material and making your own reflector will yield the best results. A properly made reflector for a side-lamp orientation, such as the one shown below, can direct almost 100% of the light toward the screen.

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