so would this be bad for the fish? bad for the tank? bad for anything? i think it makes my goldfish look more gold.... hes about 7 years old now i dont want to risk killing him if the HPS is bad for fish

the lamp sitting on the aquarium is a 70W lamp (the lowest i got) the lowest metalhalide i got is 175 and the lowest MV i got is a 175, i'm scarew of the other two options because of the UV emitted by mercs, and the overwhelming brightness of the MH, plus the MV bulbs are too big to fit in the existing FL chassis

also how would the HPS light affect his pigmentation? would it be bad or would it help (i think i have not been giving him enough light to be honest), i never turned the aqarium light on, figured it was un-needed, but then my aunt came over and called me on that.... always wondered why he was pale...

I don't know if it's good or bad, but I've seen lots of those dual arc tubes being used to light up fish tanks, and they use MH and HPS and some of the MH are very high color temps like 10 to 20 K, so I don't see it being that bad, just watch you don't heat the water up to much ..

He will probably be fine but if I were you I would use no more than 35w and I would also use some 6500k CFLs.

I would think a HPS light would make for a strange looking aquarium.The dual arc tube lamps are favored  by plant growerts in plant grow lamps-combines the advantages of amber sodium light(sunset-sunrise) with the daylight quality of halide light.Thats at least what the plant guys say.Never heard of the dual tube lamps used for aquariums.

Don`t worry about the mercs, we use to have a large aquatic place in our neighbouring town called Stapeley Water Gardens, they had a huge freshwater fish area, with loads of large tanks for every type of tropical and fresh water fish you could think of.

All the tanks were lit with 125watt mercury reflector lamps in special hood fittings, with some coloured fluorescent tubes thrown in for extra effect!
I use to have a 5 foot by 2 foot tropical fish tank, (sorry no pictures though), and lit it with exactly the same lamps!, MVs look awesome on a tank enviroment.

I think HPS would look weird and un-natural on an aquarium ... but it would certainly highlight an orange fish

I'm pretty sure the pigmentation on fish works like tan on people - its the deep-blue/UV light that does it.
I had some koi in a tank once, and they basically outgrew the tank .lol. so to help prepare them for their eventual move out to the yard, I started increasing light on the tank, including putting a Actinic-03 lamp (deep blue & puts out some UV if you havent seen one) .. I also noticed with time the fish's colors got deeper (& even more once they were outside).

Don`t worry about the mercs, we use to have a large aquatic place in our neighbouring town called Stapeley Water Gardens, they had a huge freshwater fish area, with loads of large tanks for every type of tropical and fresh water fish you could think of.

All the tanks were lit with 125watt mercury reflector lamps in special hood fittings, with some coloured fluorescent tubes thrown in for extra effect!
I use to have a 5 foot by 2 foot tropical fish tank, (sorry no pictures though), and lit it with exactly the same lamps!, MVs look awesome on a tank environment.

alright... if i ever find a smaller mercury bulb i may try it sometime.... or maybe i can just ditch the original FL chassis then put a 175W merc in.... although idk if the top of the tank can support a ballast, remote ballasting is an option but i like to avoid that with my builds if possible, i think what i'll do for now, is have a CFL and  a HPS lamp, until i get access to more resources then i'l change the CFL to like an 80W merc, does it matter if the merc clear or coated? does one or the other look cooler?

i might actually hold off on this idea.... all i have is a 70W HPS and a few minutes later after taking that picture my fish was hiding behind the heater...

  remote ballasting is an option

Actually for HID lighting that is a very good option - it gets all the heat they generate away from the tank. [/quote]

after taking that picture my fish was hiding behind the heater...

Goldfish shouldn't have a heater!

oops.... wait they shouldn't? why though? it gets awfully cold during the winters (atleast for a fish) here, thats why its in there... hes had it for like his entire life...

oops.... wait they shouldn't? why though? it gets awfully cold during the winters (atleast for a fish) here, thats why its in there... hes had it for like his entire life...

They're cool-water fish, not tropical. So even cooler 'room-temperature' in the winter is good
 
I've got a few Goldfish (along with Koi & some sorta Carp)...outside, and in the winter the water freezes over (pond is deep enough not to freeze solid ofcourse + I keep a pump circulating it). The fish can sorta hibernate, its actually in their natural cycle.

But if your fish is multiple years old, should be kept as is for consistency.