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Hello

Need some advice on the appropriate amount of light for a 48L x 18W X 20H (75 gallons) planted fish tank.
Currently running 110 watts of lights (flouros) but keep on seeing that the recommended amount is 3 to 4 watts per gallon is this correct.
Would this amount of light cause an outbreak of algae.

thanks

fox

Hi,
With 110 watts on a 75 that is about 1.5 watts (rounded up)
and OK light for most low light demand plants. How much
more wattage you should/might use depends upon what you
want to do with the tank. If you want to stick with
low light plants and fish, then leave things alone.
If you want to have a tank without things like CO2
injection (perfectly OK) then stay around 2 watts/gallon.

If you really do not want to be confined by what plants
you would put in the tank, or if you are planning on using
CO2 injection, then wattages that you mention (3+ watts
per gallon) are necessary.

It is not necessary to go that high in watts per gallon,
nor is it necessary to go to CO2 injection.

What do you want to do with the tank?

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

hi Frank

Basically want to grow more than crypts and java ferns at the moment.
If went to 3 watts per gallon would i have to look at co2 injection or not

fox

CO2 makes it a lot easier on you at 3wpg(or 2wpg), but is not necessary. However, I'd personally get CO2 for that much light. At 2wpg you can grow a lot of different plants and the need for CO2 is less.

More light does mean there is a greater chance of growing a lot of algae.

---

Critical Fertilator: The Micromanager of Macronutrients

Hi,
For the plants that you want, what you have now will work
for most of them. One way to improve things would be to
get a different lighting assembly. At 1.4xxx wpg you are
on the "edge" of things but 2 wpg would be much better.
Things are also complicated a bit more because of the
depth of the tank. Lights in the lower Kelvin ratings
do not penetrate the depths of the tank with as much
intensity still intact because light in the lower Kelvin
range is easily absorbed. In a taller tank, the light is
also easily scattered. Generally speaking tanks that are
24 inches tall should use lights in the 8-10K range, with
yours at 20 vs 18 inches you might see a difference by
shifting the K range higher.

As far as injecting CO2 is concerned, at this point you
do not "need" to go to that expense. Plants need several
things to grow. Among them light and carbon are two very
major items. If you were to up your lighting so that you
had, say, 3+ watts per gallon, then you would need to add
extra carbon. It's kinda the difference between giving
them what they need, in the quantities that they need.
If you up the lights then with that excess light they will
initially grow very large and fast, with lots of new
leaves. But, if you don't also give them the Carbon in a
form that is easy for them to use, then you will stunt them
and the conflict between driving them with excess light
and starving them with lack of nutrients will eventually
cause them to yellow and die.

Honestly, you can have a lush green jungle at 1 - 2 watts
per gallon and without the CO2, provided you are careful
about what plants you use. Low light plants would thrive
at two watts/gallon, and many of the medium demand light
plants would thrive.

Were I you, I would raise my wpg to 2 watts and start
enjoying a planted tank.

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--