what to use to fertilize

i have had several types of plants in my aquarium and they all died. i waited about 2 months or so and now i added another unidentified plant in my aquarium. what can i use to fertilize the plant without killing fish or ruining water perameters? and something that is not expensive please!

all my tanks are planted and i have no problems.
More important than fertilizer is light. if theyre not getting enough lite they cant photo synthesize. i just have the standard fluorescent bulb that came with my hood but want to go out and get a nutri flourescent to help my plants more. plants also need co2. fish provide some co2 but not enough for alot of plants to fluorish. if you have the money you might want to look into a co2 set up with co2 tanks and all. it can be pricey but worth it . if your a poor college student like me then the best way to go is the yeast co2 set up. where you make your own out of a couple of household bottles and cooking yeast for your co2. there 's alot of documentaion on the internet about this method. I also use a liquid fertilizer that contains chaleted iron which is necesarry for plants to grow. iv'e found that the instructions on the back to use with every water change and every two weeks is excessive and has caused rapid algea growth. plants are a living organism and much like fish need the environment around them to suit their individual needs. find plants that match the same water parameters as your fish or vise versa. other than that iv'e heard of people using laterite under the gravel or fertilizer tablets under the substrate next to the roots but if not carefully watched and managed ferilizer tablets can leach into your water and leterite will cloud your water as well if not properly placed. good luck.

Good freakin answer utafish.....

thanks utahfish, can you identify this plant for me? no one else can!

Just a guess, but it sort of looks like some sort of hedge.

i dont know what kind of plant that is. it kinds looks like a type of crypt but who knows, sorry.