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is that enough light

1023 Views 11 Replies 6 Participants Last post by  Hoppy
hi all,

i have a 75 gal bowfront with a newly planted bed of glosso. just changed my ligthing from a 196w compact to a 216w t5 HO. tank is also on tank co2.

is that too much light or too little light?

there has been a lot of algae growing once i got the t5. should i remove one of the bulbs and go with 162w?

lastly, i like how the tank looks with a actinic blue light. if i were to go with one actinic 54w and three 54w 6700k t5 HO would that be good enough? would the actinic promote algae growth?


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I would say that you have too much light. You didn't say anything about fertilization (which you will need, given your current lighting). It is good that you have pressurized CO2 already.

If you like actinic light, then you can use one bulb, but know that it will not do anything for your plants.
considering the size of tank and the plant, how much light is enough? 108w or 162w?

any recommendations on fertilizers?
I had 220W of T5HO and had lots of problems with algae on 110g. Now im on 110W and its much better. With 75g i would go with less that 100W, maybe 2 T5NO

For fertilizing go with diy EI
EI (estimative index) is a method of dosing fertilizers to your plants. In high light aquariums, plants will use up the available nutrients in the water very quickly, so as a result, we must provide it to them.

There is more information regarding EI dosing in the stickies that are at the top of the "Fertilizer" subsection of these forums.
In deciding how much light your tank needs, don't think about watts per gallon. Instead think about how far from the light the substrate is. If your tank is 48" x 18" X 22", the light will be about 22 inches from the substrate. At that distance a T5HO bulb, with a single bulb reflector made of highly polished aluminum, will give you low medium light. Two bulbs close together will give you high light. Any more than that will give more light that you are likely to be able to manage. A pair of T5NO bulbs, with the slightly less effective reflector typical for them, will probably give you about the same light as the single T5HO bulb. Your tank is 18 inches front to back depth. That makes it difficult for a single light to evenly light the whole substrate, and plants would all grow towards the light if you did use it. So, it is better to use two T5HO bulbs, widely separated, or two 2 bulb T5NO lights widely separated, to light that tank. Or, many of us like to suspend our light a foot or so above the top of the tank. This makes maintenance easier, gives more uniform lighting throughout the tank, and makes adjusting the light intensity as easy as raising or lowering the lights a little bit. If you do that, you could use a 4 or 6 bulb T5HO light. You will use more electric power than necessary that way.
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T5 HO's are bright lights especially with a good reflector. Watts per gallon rule does not apply to them. If you are having algae problems then raise the lights or remove a bulb or put window screen on the top of your tank.
1. what is the difference between T5HO AND T5NO?

2. does the actinic blue light contribute to algae growth?
T5ho- high output
T5no- normal output

As for 50/50 bulbs I think they had no purpose in a planted tank
but does the actinic blue contribute to aglae growth?
All light contributes to algae growth, and to plant growth too. If there is enough PAR for plants, they will use it. Algae are just less picky about all parameters than plants. I haven't seen a good controlled experiment that demonstrates whether or not actinic light helps algae more than plants.
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