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I have my bettas in a 2.5 and 3 gallon respectively. Both were lit by 15w incandescent lights. These heated the tank water in no time so I had to limit their use. This was bad for the sagittaria subulata (dward narrow leaf) that I added in both.

I found a 10w flourescent mini-compact and it fits well. However, it is comparable to a 50w light. Can I run this light for 6 hours daily, rather than 8 or 10 and get the same benefit for the plants? I'm concerned about an algae bloom at that level.

I'm planning to move these guys to a 5.5 or 7 gallon with a divider, but that won't be immediate.

Cory -
I have found that compact flourescents work very well. But as you said, you have to keep in mind the high output of such a bulb. On my 25g for example, I recently set up a clip-on light and it has a 23w spiral flourescent "daylight" in it - which is equivalent to 100 watts. Just minimize the time it is on , enough for the plants, but not too much to grow algae or burn the plants.
I would say a 6 hour "daylight" period would be sufficient for your plants and if you find that either algae grows, or the plants are not growing, adjust the hours of light accordingly!


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I believe when it says it is equal to 100 watts, or whatever, it is refering to incandescent lights. You don't really look at that value when deciding how many wpgs and such the tank has.

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Always use the flourescent wattage when calculating. The incandescent equivilant is useless.

Also bear in mind the wpg thing is like the inch per gallon "rule" - more like a guideline. And like that it falls apart a bit when it comes to small tanks.

If you think about watts have nothing to do with light intensity. It's about the power used to drive the light. It's assumed that a higher wattage will produce a brighter intensity, this is just an easy way to measure the lighting requirements and easy to understand how many bulbs are needed.

Where it falls apart in the small tank is that for an example you can put a 10 watt bulb over a 5 gallon tank and technically you have 2wpg BUT you still only have a 10 watt bulb which is really not that bright. So far small tanks you really need to aim a little higher in wpg.

I would say a 10 watt bulb over a 2.5 or 5 gal tank is fine. I've got 2 9 watt bulbs over my 5 gal with no problems.

Leave the lights on for the full 10 -12 hours cycle. Reducing that is detrimental to the plant. They need a proper cycle, it's take's plants a few hours to get started up when it comes to photosynthesis. That's why you will usually just see the plants begin to pearl late in the afternoon or evening - they need time to build up a good head of steam.

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What I'm doing is cycling the time. I have the light on for about 2 hours in the AM, then I let it rest a few hours, then it comes back on again. I do this 2-3 times. I'm going to set up a timer to have it go on and off. One of the reasons I'm doing that, is because I have not read anything that tells me I can use the coral life 10w mini-compact in my Aquatic Gardens aquarium. The bulb goes into a sealed in area with little venting and I can feel the vents get quite hot. However, I'm sure it gets even hotter with the incandescent bulb.

I've also heard that algae can't respond as quickly to lights going on and off like plants.

This tank has no co2 and is only lightly planted with two sagittaria's and one java fern (which happens to be making lots of babies atm).

Once my crypt willisii takes in my 20 long, I'm going to steal some of that and plant it in the betta tanks.

"I've also heard that algae can't respond as quickly to lights going on and off like plants."

I've also read that somewhere and to be honest, I'm not convinced. As Bensaf said, you can actually see in CO2 enriched tanks that the plants take several hours before they kick off and begin producing bubbles, so I don't think plants respond at all quickly to lights going on and off.

As for the claim that algae can't respons as quickly to lights like plants, it goes against my common sense. Why would algae be quicker to respond to anything else but lights? The nature of algae is to take advantage of situations less favourable for plants. I'm not saying that having your lights on for intervals of two hours won't help fighting algae, what I'm saying that if between plants and algae, if anything could take advantage of this, it would be algae.

If that was the case I think all of us with planted tanks would be having our lights on at intervals by now. Well, it could be a nice experiment anyway. Let us know if does work.

Last edited by untitled at 14-Apr-2005 11:23

I think i got too much lighting in my tank.

Tank Capacity
Litres: 33.63
US Gallons: 8.88
UK Gallons: 7.4

Lighting is 2 X 30watt 6500K plant tubes, so i guess 60watts?

60/7.4? = 8.10w/gal?

Tank Dimensions are 18inch long, 9.5inch wide and 12inch high.

...And this refers to the topic at hand how? Also, yes, you have more than excessive lighting, which is asking for an algae bloom if parameters even slightly step out of line.