Metal Halide Distance from Water Surface??

[leroyfong]

After my 5ft tank's silicon gave way few weeks ago, i have gotten myself a new 5ft x 2 x 2 tank replacement as well as 2 metal halides bought from a fellow forumer. This gave me a chance to rescape my tank.

I customed my metal halide stand where the 2 halides sits above the tank. They are 150W each with 6,500K and is raised to about 12.5 inches above the water surface.

There seems to be lesser pearling when I switch to the metal halide compared to my previous 36W PL x 9 + 40W FL x 2 = 404W.

I am wondering if the height of 12.5 inches is too high.... Would like to have some advise on the ideal height above the water level for these metal halides.

Thanks,

[hirowen]

Hi,

I used the AQ's tank calculator and calculated that you need 449 watt for ur big volume of water. Maybe you can try lower the MH. It will more or less help penetrate deeper into the water.

[plantmania]

Since your metal halides are 2nd-hand, have the bulbs being used for long (6mths or 1 year or 2 YEARS)? It could have most of its intensity and almost time to change them the metal halide bulbs...... Quite good already since some of the plants still show pearling

Since you just rescaped, another new balance of fert regime, water quality , etc , must be considered. Once stable, your plants should flourish...

[vinz]

You just setup the new tank, right? The lack of pearling could be attributed to other factors. Consider that.

If you want to see if it really is the MHs, and you still have your old light set, try putting those up and see if the plants do better.

With MH you do not have to follow the 3WPG guideline. Just make sure you have enough MH to cover the tank. In general, 1 MH can cover a 2x2 sq ft area, give or take a few inches. You can always layout the tank to fit the light cast pattern.

[hirowen]

[quote:d7126231f8="vinz"]You just setup the new tank, right? The lack of pearling could be attributed to other factors. Consider that.

If you want to see if it really is the MHs, and you still have your old light set, try putting those up and see if the plants do better.

With MH you do not have to follow the 3WPG guideline. Just make sure you have enough MH to cover the tank. In general, 1 MH can cover a 2x2 sq ft area, give or take a few inches. You can always layout the tank to fit the light cast pattern.[/quote:d7126231f8]

Hey hey! I think I learnt something new again!!

[leroyfong]

These are pictures of how the MH has been placed by a custom-made stand.

Before the custom-made stand was finished, I was running the tank with my PLs first and so I know that the tank was pearling.

Anyway, there are already signs of hair algae growing in the tank. So I am starting to dose fert NO3, PO4, and Fe+traces. I have also increased CO2 to 30ppm maintaining at KH of 4 - 4.5.

There are signs of pearling today. I supposed the lighting is enough becoz the glosso are growing sideways instead of upwards.





Regards,

[leroyfong]

http://www.imagestation.com/album/?i...ulation_page=Y

sorry can not show pix. Link as above on MH custom-made stand.

Thanks

[vinz]

It seems that your ImageStation album is protected with a password.

[IUnknown]

Here is a thread with some problems I was having with my MH spread, it is for a 70W.
http://aquaticplantcentral.com/forum...pic.php?t=2757

[leroyfong]

Vinz,

Have taken away the password. hopes it works now. Let me know if it doesn't.

IUnknown,
Thanks for info. Insightful about these details which I have thought about but not act on it.

Regards,
Leroy

[vinz]

The album is working now.

I'm rushing out, so a quick reply. You tank is still quite low in plant load. Once it gets denser, it might start pearling. The current load probably isn't producing enough oxygen to saturate the water really quick.

Still, this does not cancel out the fact that your plants were pearling with the previous set of lights and not this set.

Are you running a chiller? If not, any difference in water temperature between this set and the previous set of lights. Water temperature affects tha gas saturation point of the water and that may explain the lack of pearling.

At the end of the day, what's important, to me at least, is that the plants grow healthy, not too fast and with minimal algae problems. Pearling is secondary to me, though I must admit it does give a sense of satisfaction.

[leroyfong]

Noted taken. Definitely using the PL has generated more pearling than the MH. But as you have mentioned, it might be due to various reasons.

Think my impatience has overwhelmed my reasoning regarding the pearling. I was just worried about not enough lighting reaching the plants due to hanging the MH too high. THere was not much discussion about recommended height to hang MH above water surface within the forum.

It seems that 1ft and above is fine, and importantly is the distribution of the MH lighting which is another important aspect often missed out.

Now I can see glossos pearling, so should not be the MH hanging too high. Light penetration should be sufficient. I have also started dosing NO3, PO4, and Fe+traces.

Added yamatoes to clear hair algae growing all over the plants. They are fantastic workers clearing all the hair algaes within 2 days + increasing CO2 injection to reach min. 20ppm. I am using 2 DC fans to blow. One running 24hrs and another during lighting period only.

Regards,

[terkar]

My MH lights are about 20 inches from the surface. If you have plants that stick our of the water, they'll burn. Pearling still goes on. Will post pict soon. Its me Merv.