Last week I turned the 40 watt fixture off and left only the 96 watts pc lamp on my 20 inch cube.

total 96.

today I turned ON the 40 watt and swapped out the 95 pc fixture for a 28 fixture I had in my closet.

INTENDED TOTAL pc light... 68 over 30 gallons but

it turns out that the 28 watt fixture had a 50/50 bulb actinc/daylight. so actual light right now....

54 over 30 gallons.

I have ordered the better bulb from big als and it should be here in a few days.. My question is am I better off leaving the 54 watts going for now (pc spits out more lumens than T8s anyway).. OR should I go back to the 96 watts until the new bulb comes?

I know I am asking a lot of questions, but I am also taking a HUGE leap of faith!!! yet another on this board and I hate to wreck the tank I"ve jsut pulled back from a co2 bba disaster. Thanks

I have toninas and red plants and really want my tank to keep functioning as a high light tank.

Tom, how low is too low? and for a few days, which is best a little less or a little more?

btw. the cardinals are amazing in a less well lit tank, gorgeous color!!

Actinics spits out alot of PAR but no lumens to speak of. Leave it in until the new bulb arrives.

With 68 watts well reflected daylight and actinics down on a 20x20 inch square you will get around 130 mmols/m2 - Thats what I call high light and for example what Oliver Knott seems to prefer. Don't think anyone call his tanks low light =)

Americans will call it moderate light and what Tom Barr usually speaks warmly about as "less light". Easier to maintain but will grow any plant.

Lumens is yellow light contributing to PAR but not much PUR since plants can't use yellogreen light very efficiently - so forget lumens.
For example, an actinic and a red bulb will give you very low lumens but a lot of photosynthetical usable radiaton. That's why grolux bulbs feels dim (they put out mostly blue and red).

Defdac, will the 54 watts be enough to sustain the tank til the new bulb arrives or would I be better off putting the 96 watt fixture back on until I can bring it all up to 68?

and thanks!!!!

Then you will only get around 100 mmols/m2. Will probably work, but I feel more and more after running alot of numbers of well run tanks that 120 mmols/m2 at the bottom is the magic threshold for good pearling and the ability to hold down H. callitriciodes for example.
Going down to 80 mmols/m2 is definitely pushing it down where you will limit yourself plant wise.
If I'm not mistaken some high light plants have their light compensation point at about 80.

(Oh. I'm talking PUR-values here btw. PAR-wise you will get 200 mmol/m2 with 54 watts and over 240 with 68 watts.)

I am definately rising to the 68. and I feel really good seeing that your math shows that will be a good amount.

My only remaining question is what will be best for the short term, while waiting for the new bulb.. 54 watts or 96 watts. I figure Big Als will ship monday and I"ll probably see the stuff on wednesday/thursday.

I would go for the 54 watts (or switch in the actinic again to 68 watts).

96 watts will be like over 345 mmols/m2 PAR and 185 mmols/m2 PUR. Not only is that very much light - the fixture must be like over 36 inches, so I guess not all of those mmols can be directed down in the aquarium..

The actinic is still on .. I just didn't think it counted.

the 96 wat fixture was 20 inches.. it was a quad bulb 18 inches wide with four bends so the light did all hit the tank.

keeping the two smaller fixtures on ... and awaiting the new 28 watt all daylight bulb to bring the tank up to an honest 68 watts. .. and praying just a little bit that my plants don't hate me.


Thanks so much