When you stated that you do water changes once monthly, but have been busy at school I'm assuming you haven't done a water change in a few months. What you are dealing with now is referred to as old tank syndrome. The waste products that build up will usually drop your pH, and increase your hardness and TDS. This means the water in your tank could be way different from your tap water, and doing a large change could be very stressful, if not deadly for your fish.
I wouldn't do more than 10% to 15% daily, these daily water changes will acclimate your fish to your tap water gradually. Use a water conditioner that takes care of chlorine, chloramine, and ammonia, as chloramine is a combination of chlorine & ammonia. Feed 1/3 to 1/4 normal, less food means less waste.
Chemicals like Ammo-Lock that say they remove ammonia don't actually remove it, they convert ammonia to ammonium, a compound that is harmless to fish but used the same as ammonia by your bio filtration. Shops that do aquarium maintenance as part of their business use Ammo-Lock all the time, it is a good product.
After 5-7 days of the smaller water changes you can get on a schedule of doing weekly changes of 25%. What you really need to do is find out what is causing the ammonia reading. The most common ones are replacing filter media, or rinsing it in tap water, topping off with water that hasn't been treated, or overfeeding to the point that your bio filtration can't handle the extra ammonia produced by the rotting food.