I want to setup a 2' tank this weekend. Most of the flora would be Hairgrass. The tank volume is between 12 to 15 gallons. I will fertilize along the EI method.

1) My CO2 regulator is the one without the solenoid. I have heard that with non-solenoid regulator, it would best to just leave it on even after photoperiod. Or should I turn off CO2 after photoperiod and turn it on again the next day just before photoperiod?

2) This wil be an Iwagumi type tank with lots of Hairgrass. I am thinking of using 2 x 18W PLC or 1 x 36W PLL . Would this be too much light for this kind of setup?

Please advise. TIA.

i think hairgrass needs a bit more light than that to really excel. correct me if i am wrong, but i believe that you need a certain minimum light level with tanks [especially small ones] to be effective. i know i have never had luck growing hairgrass but that could be a number of different reasons.

Well with 36W over 12 gallons, that's 3WPG. How much more does Hairgrass need to thrive. Please advise. Thanks.

A 12 gallon tank is too small for the "2 watts per gallon" rule to mean anything. You need more light for smaller tanks. But, 36 watts of an AH Supply kit is most likely enough for that tank. (I think)

Thanks for the info Hoppy.

But when we classify a tank as small, how small is small ? And how many WPG should a small tank be equipped with for low, medium and high lighting. Same goes with large tanks.

T5 bulbs in individual reflectors provide more light intensity than T12 bulbs with flat, white painted "reflectors". So much more that any "rule" would have to be different for the two bulbs and all of those inbetween. If you start with about 2 watts per gallon of AH Supply light kits for a 20 gallon or bigger tank you would be in the ball park for having moderately high light intensity. Tanks below 15 gallons or so, need more for the same intensity. That is the best I can do!

My experience also tells me that a light fixture that is smaller than the tank - shorter bulb or with the light not spread out front to back - will have a much higher light intensity right under the light and lower intensity in the outer areas. So, a 40 watt fixture over a 20 gallon tank could have the equivalent of 3 watts per gallon right under it if the fixture was much smaller than the tank top.

I think this means you really need to do actual intensity (PAR) measuring in the tank with the fixture in question to really know the answer to your question.

2x18w is plenty of light to grow HG in this tank, or any foreground weed.

I know, I've done it(about 10 years ago).

Regards,
Tom Barr

Sorry to dig up this thread tom, just wanted to recap on it.

So in the instance of trying to grow hairgrass with this tank and this amount of light if someone where to fail growing it... while they were dosing EI and injecting co2.. and the plant does not grow... a full lush... lawn .. what could the problem be.

It's not the light.

Here's HG at 1.5 W/gal of the same light type(T5s)



Go back to CO2 most likely.

Regards,
Tom Barr