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So, I've given up on the idea of a fancy planted tank in favor of low-light plants like anubias and crypts. I've also been trying to get bolbitis ferns to grow, but I suppose that's a topic for the planted tank forum.
Since the new plants don't need that much light, I have a HUGE algae problem. There are currently only 4 little fish in the tank, so I don't think high nitrates are contributing to the problem. I have a tallish piece of driftwood in the middle and where it is closest to the light, it has sprouted blankets of bright green algae that spread out and actually shade the rest of the tank. I pull it off, but within days it comes back.

My problem is clearly that I have 130 watts of light over my 30 gallon tank from my very expensive compact fluorescent fixture that I bought for the more demanding plants. I've even removed one of the tubes so there is only 65 watts, but it's also a 10,000K daylight bulb. Would a 6,500K bulb be better? Do I have to buy a whole new light fixture that won't put out as much light? Is there anything else I can do that will help?

Hoping that there must be a word for everything I mean...

Hi,
First, here is a link that you may, or may not have seen:
http://www.aquahobby.com/garden/e_bolbitis.php

and another:

http://www.aquahobby.com/articles/e_lowlight.php

and to inspire you:

http://www.aquabotanic.com/dutchsecrets.htm

You don't mention what you do have in the way of plants in
the tank now. You started out with 4+ wpg, and unless you
had huge amounts of fast growing plants, and injected CO2,
you were doomed from the start. If you are going to drive
the plants with that much light, then you have to furnish
the nutrients necessary for growth and survival. Carbon is
the main nutrient, followed by the other macro and micro
nutrients.
If you are going to "Zap" a small tank with that kind
of light, then you should be experienced in aqua gardening,
plant the tank with fast growing plants, as well as plants
that demand that kind of light and furnish it with a
bottled CO2 injection system. That is a huge amount of
light on a shallow tank.

Needless to say the tank is out of balance and the algae
is filling the niche. 10,000K is way too high in "K"
rating for a 30G freshwater tank. As has been mentioned in
other forums, 10,000K is the low end of Saltwater reef
tanks, and the "extreme" top end for a freshwater planted
tank. It is at the "bluer" end of the spectrum, and as
such the light is more intense and that intensity will
travel through the tank to the substrate with little
scattering and absorption. It is a harsh, bright light,
that can begin to affect how we see the colors in a
freshwater tank. It can start to "washout" the greens.

I would suggest the addition of some floating plants to
provide shade and to begin absorbing the excess nutrients
in the water. I'd also add fast growing stem plants, lots
of them, before you add any (more) slow growing plants.
The slow growers that you mention will simply become
encrusted with algae and it will eventually smother the
plant it will grow so thickly. Water Sprite, or Water
Wisteria would also be a good, fast growing plant that
would thrive in the tank.

Your current rating of a "tad" over 2 wpg is good, but I'd
still argue that the light is "wrong." If you are
determined not to pursue the higher light tank, I'd
switch to the lower "K" rating bulb(s) that you mention.

I would still use the Wisteria or Sprite I mentioned as
well as several bunches of fast growing stem plants.
I would remove the driftwood, scrub it, and then attach
your desired ferns or mosses to it, and place it back into
the tank. I have a 30G tank and I have (currently) one
65 watt, 6700K bulb running for 10 hrs/day. Each week I
throw out handsfull of plants. Perhaps the only difference
between our tanks is that my gravel is 100% Sea-Chem brand
Fluorite and I'm injecting CO2. If you want to stick
exclusively with the low light plants you mentioned,
then you might probably have to drop another "notch"
to 1.5 wpg.

Frank
PS. Planted Aquaria, might be a better place for this
discussion.


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

Hi Frank

Thanks for the links! The bolbitis has been giving me nothing but trouble, and that helped.

Almost three years ago, I endeavored to set up a heavily planted tank with fast growing, light hungry, nutrient devouring plants. I was using DIY CO2 and Flourish Excel for carbon, and the rest of the line of Seachem's plant supplements for the remaining nutrients. My problem was that I could only keep the tank lush, beautiful, and stable for about 6 months at a time, because the minute I got just a little lazy and didn't dose ferts on time or didn't take time to trim my jungle, the balance would get way out of whack very fast and it would be difficult to get things back in proper order. The tank was lovely and very rewarding when things were going well, but I simply can't keep up with a high-maitenance planted tank at the moment.

So, that is why I have chosen to go with a lower light tank planted with ferns, anubias, and crypts. However, like you said, even the high K 36 watt light is toasting the plants on the tall piece of driftwood and inviting algae. I have another tank planted completely with anubias on bogwood, and I have to keep the top covered with a layer of floating salvinia to suck up nitrates and diffuse the light. Because the piece of wood in this tank reaches the top, I'm not sure even floating plants would help enough, though I certainly have plenty of salvinia left over to give it a try.

I guess my question was simply if a lover k-rated bulb in the same fixture would bring down the light intensity enough for my low-light plants, or if I should think about getting a regular fluorescent fixture with lower wattage.

Hoping that there must be a word for everything I mean...

Hi,
Yes, I think that the 6700K bulb would help.
The 10,000K bulb is too "bright" and the 6700K would
help.
Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

Changing the temp is just matter of personal preference and what you want the tank to look like. Different K rating in the 5500K -10000K range will grow plants fine its just matter of what colors you want to bring out in your plants and/or fish.
If you don't want to change to a lower wattage fixture, I think you may want to go with some floating plants like salvinia or something like that to shade the slow growers. I have some if you would like to go that route just PM me.

As,for bolbitis you need to provide that with current for it to thrive and grow, try placing it near the outlet of your filter and see if that works out for you.

Good luck, and I agree with Frank the 6500K would be a better choice 10K is a bit too far up the spectrum for my liking used alone. 6500K and 10000K combo is a nice pleasing mix.