What kind of light bulb (fish tank)?

The daylight bulb is fine.

The reason your ferns died is because they dont have enough watts. It's not the kind of light, its how much light. As the other answerer mentioned.

C02 systems are totally easy one bottle lasts about 2 weeks before you even have to touch it again. But that's another story.

You have some medium light plants that will need 2 to 2 1/2 watts of light per gallon of water. this means you need 40 watts of light and your only getting 18. not even 1 watt per gallon.

the light that came with the hood is most likely NOT a 'daylight' bulb. Those are basic basic 'lights' with little or no light spectrum that your plants need.

You need light in the red and blue's of the spectrum for the best growth. (around 6,700 K) I suggest Petsmart's bulb named Life Glo II it's the PERFECT watts, lumens and spectrum your plants need. They are twenty bucks for one 18" bulb but if you add another light strip and one more bulb you'll be just fine and can grow just about any plant you want!

Lowe's does sell a 'grow bulb' in the red and blue spectrum, but there are no listing for lumens, or Kelvin and I have not yet give this one a try. It's half the cost of the Life Glo.

Whichever bulb you choose make sure it has Kelvin between 5,550 and 7,000 closer to 6,700 the better, this simulates high noon which freshwater plants need.

Good luck!

Adding another reflector with the additional bulb may be of more benefit than changing the bulb you have. Unless you can afford some of the high intensity lamps, your plant problems may be due not enough light. The full spectrum bulb gives you the most natural light. It may not be bright enough.

attempt shifting it clock sensible and counter clockwise jointly as screwed in, sometimes it purely desires a sturdy connection. yet.... purely considering you purchased it new does no longer propose the bulb is sturdy. attempt shaking the bulb close on your ear. in case you hear some thing shifting around, it may be no sturdy. attempt finding out the actually unit besides, perchance positioned a usual bulb to work out if it works or no longer. sometimes, water will can get in the compartment.