Testing water quality

Question

My tank   "I have a 45 gallon tank with 4 small angel fish and on Sunday just added a small pleco... Initially I cycled the tank for a month and added my angels in November and everyone is doing great so far and I want to keep it that way.   My question is what should I be testing for weekly and how do I do that?  I currently have a ph test and an ammonia tester both in dropper form.  What about water hardness, nitrate cycle, or other water parameters that I may not be aware of that I need to keep an eye on?  What is essential I continue to test and how do I do that since I don't see anything other then your generic ph at pecto.  
Also how many times a day should I be feeding them. I heard 2 since they are small and growing but I don't want to over feed them.
Thanx!"

Answer
Alright you might have some problems with the angels. I am going to be blunt with you here, Angelfish get to the size of a regular piece of printer paper. Very tall.

4 angel fish cichlids will start to get territorial if they don't stunt first in a small aquarium then they need. 1x Full grown angelfish stocks your aquarium. If they start to pair off most of the angelfish will die as they will attack each other.

If it is a Common Pleco you will need to return it. Common Pleco's grow to 2-3 feet and need a 100+ aquarium.

This is my advice but it is your aquarium and your pets so you do not have to listen.

Okay...

You need to test for the following:

Ammonia should be 0 PPM - Ammonia is highly toxic and can burn the scales and gills of your fish

Nitrites should be 0 PPM - Nitrites is toxic as well

Nitrates should be 20-40 PPM any lower or higher then that is considered toxic. If you have high nitrates small water changes helps.

PH should be 7.5-8.0

Hardness depends on where you live

API Test Master is the most accurate it is 30 dollars but it works for 180 tests.
It comes with instructions so you can read how to test on the back.

You should let your fish fast. So 4 days out of a week. 2x a day preferably morning and night.

Your fish need a variety of food.

If you decide to go ahead and keep the Common Pleco - Algae Wafers and green vegetables such as zucchini, cucumber, squash etc. Stay away from fruits.

Angelfish - Hikari sell cichilid pellets but if these are too big you can break them up. Frozen brineshrimp and bloodworms are a good variety as well. A base would be cichlid pellets or tropical fish flakes.