i have a 29gal tank with a 15 watt light bulb...and i have about 7 plants in the tank...so once a week i add seachem's excel fertilizer...about 2.5ml with my pwc...all the plants are doing ok...not growing fast but thats not a concern since they are not dying...i was wondering if thats enough fertilizer...i read somewhere that too much fertilizer will kill the fish...since my plants are growing so slow i wonder if they are using all the fertilizer that im adding every week or its just building up in the aquarium...TIA...