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Mercury Vapour or Metal Halide??
I wrote to this list in december last year about mercury vapour light. I
got the general impression at that time that people from US did not use,
did not know much about MV light or thought that MV allways was bad for
The content from my message to this list was merely to inform everybody
that there are different types of MV bulbs. It is the same thing as with
fluorescent tubes, there are also several colour types. One of the MV
types is the world known "street light colur". That colour is probably
not suitable at all for a planted tank. If you instead use a de lux or
super de lux colur MV bulb, then it looks really nice with MV light.
There are even MV bulbs specially made for planted tanks. I use myself a
bulb from Dennerle called TROCAL. It is also marked super de lux. I have
used that bulb for a year soon and I am very satisfied with the plant
growth. If you do not believe me you can look at a MV lamp in action at
Dennerle's homepage (I think it is quite new):
It is only available in german for the moment but there are some
pictures to look at.
Then to the question MV or metal halide? I can tell you what I know or
The price: In europe, at least in Sweden and Germany, metal halide
fittings are so expensive and by that reason beyond reach for normal
people. I know that marine tank people are using metal halide in sweden
but marine tanks in Sweden are very rare. The price for the metal halide
bulbs I have seen have also been extremely expensive. About 50-100 % of
the total price for a MV fitting (with bulb).
MV fittings on the other hand can be bought by normal people. They are
not exactly cheap, but in range. New bulbs can be bought very cheap.
MV wins this price battle by far.
Efficiency: The facts I have available indicates that MV bulbs is about
as good as a "medium fluorescent tube" (a normal warm white from a
hardware store). They are not so efficient as the latest tubes (TROCAL
or TRITON) but they seem to be alright.
For the metal halide bulbs I have seen facts that indicate higher or
even much higher efficiency than MV.
Metal halide wins this efficiency battle.
Colour: For a normal planted tank (my tank), the MV bulb (TROCAL) looks
very good. I have seen other MV bulbs that have looked as good. Take a
look at the web addres I wrote above and see for yourself. The plants
grows very well.
Metal halide are available in many colour temperatures and there should
be no problems either.
For a normal planted tank, MV will do the job. But I am involved in
setting up a 720 l tank for Malawi cichlids and plants. In this tank we
are using 3x125 W MV (TROCAL) and two TRITON tubes (2x58 W). The MV
lamps are actually enough for the plants and they look very good (as in
my own tank). The reason for the TRITON tubes is that the cichlids look
a bit better with the TRITON tubes. There is probably not enough blue
light in this bulb plus that there are so much colour in Malawi
Maybe if I look around more I could find a MV bulb that have the colour
needed to make both cichlids and plants look good. If anybody out there
knows about a MV bulb like that please let me know. In my tank the fish
looks very good, so for that tank nothing more is needed or desirable.
Since there are more types of different bulbs available for metal
halide, they probably win this colour battle as well. It is probably
possible to find a bulb that for instance would suit the malawi tank.
Comments and questions
1. Andy M Moore have never heard about metal halide being used in
planted tank in the UK. I have never heard of that in Sweden either. I
talked to a whole saler for Dupla. He said that it was not worth the
huge price to buy metal halides for plants. He recommended MV lamps and
he also said that metal halide was mainly designed for marine tanks (or
very large planted tanks >800 l).
2. Why are metal halides so expensive when it is almost the same
technique as in MV?
3. Are MV lamps unusual in the US? In this mailing list, people writes
mosly about metal halide. Or do people sometimes actually mean MV lamps?
Are metal halides so much cheaper in the US?
Sorry this message was maybe to long. Have a nice day anyway.