what type of liquid fertilizer are you using now? For the short term, I recommend getting 4 types of fertilizers (nitrogen, phosphate, potassium, and micro). Seachem has a line that I've used in the past with good results, Flourish. The flourish line contains many products but the ones you need to start out with are Flourish Nitrogen, Flourish Phosphorus, Flourish Potassium, and one simply called Flourish. Using these at the recommended dosage should help your tank take off while you learn more about the fertilizing requirements and get used to dosing with the stuff from Greg Watson.