I like fish emulsion -- easy to use and doesn't stink too bad. You can just dilute it about twice the suggested dilution for mature plants. Neptune's Harvest is good stuff.

@elisa

Thanks, I had thought about using fish emulsion but I'm worried about the smell since the seedlings are in my house. I don't want my cat getting too curious :/

I don't fertilize seedlings until I put them in the ground. Most germination mixes contain enough nutrients for the six to eight weeks they are in them. More is not better than enough.

If you really think they need to be fed then you can use any fertilizer you want. There is no one perfect brand. Just make sure you dilute it to 1/4 to 1/2 strength.

But as mentioned above, seedlings don't usually require feeding. It depends on old old they are, their overall health, what mix they are growing in, how long before they can go into the ground, etc.

Dave

I like to use diluted Neptunes Harvest - a combo of fish and seaweed. The aroma only lasts a short time and my cats haven't bothered it.
Keski