Improving PC Lighting in a 46G BF: two questions

[synchiropi]

So after considering replacing the bulbs of my PC light fixture, I just decided to clean the glass tank cover and wow, what a difference. Now, here are my two questions:

1. Having the cover on clearly diminishes the amount of light going into the tank, but there is just so much evaporation otherwise. I remember reading about a type of glass that is more transparent to light. Does anybody now what is the name of that glass, in other words, what should I ask for if I go to a glass shop (not sure where to buy glass in the US )

2. Additionally, my fixture contains a 10,000 K bulb. Is this preferrable to a 6,700K bulb?

Thanks!

 

[SteveDola]

From my understanding, glass covers arent exactly condusive for oxygenization of the surface water. I think that although the cover retains the condensation and inturn reduces evaporation and it plays a much larger role in not allowing oxygen exchange at the surface. This poses a serious problem for livestock. Oxygen exchange is an important aspect of the marine environment because just like you and me our fish/inverts need oxygen in the water. I would look into keeping the cover off and just doing more frequent top-offs.
Also, a 10k bulb has a different color to the light emited. In short, a 10k bulb has a more appealing white color where as 6500k bulbs have a yellower tinge but does enduce stronger growth patterns in corals. I should tell you that is the short answer...if you want to know more about light spectrums and par values you should go to reef central and look in their lighting/filtration forum---or do a search on the subject.

 

[synchiropi]

Thanks for the info on the lightning. As far I understand, 6700 K is closer to sunlight, but I guess we all like the 10,000K color more. Do you have some source about 6,500K being better at inducing coral growth?

Additionally from preventing evaporation, I like the cover because of my dartfish and wrasse. I have heard so many horror stories about fishes either jumping out or getting burned by lights that I am now very hesitant to take the glass cover out. I guess I could use some sort of net, but I just dont know yet how to efficiently cover all the little crevices.

Some of the theories I have heard about enclosed or poorly mixed gas on the aquarium water surface have to do also with building up of carbon dioxide on the surface. That, for example, is a concern for species like Bettas, which breathe atmospheric air. However, in these tanks I would think that most of the gas exchange actually occurs in the protein skimmer and sump. Given the volume of our tanks, the area at the surface is really not that significant. I have to believe that oxygen limitation is not a problem in my tank since I do not see any of the critters moving away from the bottom of the tank. I guess without some form of measurement this is my only crude way to infer this.

 

[Liam]

I would make your decision on wether to keep the glass or not based on what species of coral you are keeping or would like to keep.IMO most coral that can be kept under pc's will appreciate the extra light allowed by not having the glass.If you are worried about jumpers,go down to sports authority ,go to the fishing dept and buy the cheapest cast net they have($15 probably)make a frame the size of you tank,stretch the net over,fasten it to the frame and then trim it to size.This will not cut down on light but will prevent fried or dried wrasses
-Liam.

 

[NateHanson]

Oxygen exchange probably won't be a problem if you're running a skimmer. Those oxygenate the water very efficiently. Temperature is the biggest danger though. Even low intensity lights can quickly heat up a tank on a warm day with a glass cover acting as a greenhouse on the tank.

About bulb color - 65k is closer to sunlight on land, but under water the longer wavelengths (red, yellow) are quickly blocked by the water, and the shorter wavelengths are all that penetrates under a dozen or more feet, so the light is much much bluer down there. That's what the corals are best adapted to, so in addition to looking good, the corals will be happier with a bluer range of light.

Perhaps the clearer type of glass your thinking of is low-iron glass? Sometimes called Starfire. I don't know where you'll find it locally though. As for buying normal glass in the US, just look in the yellow pages under "Glass" and you'll find places that offer "residential and commercial plate glass". These types of glass shops are all over the place, and will sell you glass of many thicknesses, cut to your dimensions.

Nate

 

[JD46]

IMO, no matter what type of glass you keep on there, salt creep will drastically reduce the amount of light that can enter the tank. And, temp stability will be very difficult to control, especially with summer coming up.

Another option is to buy a sheet of eggcrate from Home Depot and cut it to fit the top. Evaporation will increase, but I only evaporate about 1 gal/day on my 46. It is possible for fish to jump out, but that would have to be a lucky, or unlucky as the case may be, jump.

 

[synchiropi]

Thanks guys.

I am trying to keep just soft and cady cane corals, so thats why I just have PC lightning. There might be a tank in the future where I will have mhs, but that will be in a while.

Yup salt creeping and dust are big problems. I guess I have to be better with my cleaning. Otherwise, the idea of the eggcrate is really cool and I guess it can be combined with a net to keep the tinier fishes inside.

I guess the only thing that makes me concerned for the summer is that, the possibility of my tank heating up. Keeping fingers crossed.

Thanks for the glass info. I found something online called diamant, which is a very optically clear type of glass. Incidentally, one of the tanks of the month in RC had a tank with a front made of that glass. Just think it was a pretty cool idea.