Ok explain this?

[Ranran]

I have two 80 gal long tanks plumb together into one central sump. The lower tank has three 160 watt vho 1/2 inch sand bed and about thirty pds live rock. this tank looks great. very little alge growth sand is always clean with little help from clean up crew.
The upper tank has two 175 10k halides and one 160 watt vho 50/50 no live rock and 1'' sand bed but it is plaged with cyno bacteria. The water flow is stronger in the top tank, the only difference is lights and live rock.
can old lights just over a year be the sole cause of this?
Is the little amount of live rock in the lower tank preventing the cyno? Your thoughts please.
Randy

[foobuddha]

Do the tanks test the same for phosphate and 'trates?

[Big Dave]

Originally posted by Ranran

can old lights just over a year be the sole cause of this?

There you go! You can also think of over feeding, excess nutrients, waterflow causing this cyano, but good detective work!! I bet it's the older lights. Do you alternate changing lights or do you change them all at once? I have 4 VHO's and change one out every 4-5 months or so. That way my light level stays fairly consistant (and I don't have to shell out $200+ at once) By the time I change the 4th bulb, I just keep the rotation going. Also, just a note - label the date you put the new bulb in so you know which one is next to replace. You will forget, trust me!!

Another thing that just popped in my head - does the problem tank have a lot of direct sunlight compared to the other tank? That may do it too. (oh wait - I live in oregon too, nevermind ) HTH

-Big Dave

[Ranran]

Both tanks get no direct sun , actually i hav'ent gotten any direct sun in a month.
I will test both tanks seperlty today but they are connected and share the same sump, skimmer and water. i dont expect them to be different.
Randy

[CAT]

If the water is the same (and is should be) , it's probably the lights. I changed my bulbs a couple of months ago when I had a bad cyano problem and the cyano died almost instantly -- I was netting out floating, slimy stuff for about 3 days.