fish dying, seem sick

The test I use only goes to < 0.3 the next up is 0.3. so I assume that it is almost at 0 but I have no way of checking
What are some good tests to buy (brands) ?
 
I use the Aquarium Pharmaceuticals master liquid test kits. Do not rely on the test strips.
 
I notice that a lot of you who give the advice have real plants. My tank does not have any real plants and does not look nice at all. It has this really ugly big thing in the center that the ghost glass cats hide in all the time and 2 little ones on each side that the fish don't really go to at all. I am thinking that if no more die and my nitrate levels are fine and they start acting normal again that maybe I should plant some real plants. What would be good to plant?
I just have gravel on the bottom. My surviving fish are as follows:
2 ghost glass cats
1 weather loach
1 red platy
2 neon tetras
2 alino catfish
My tank is a 25 gal. and I was told I could get more neon tetras, platys,a nd maybe another type.
Any advice on whether I should get more fish eventually and what type of real plant life to get? I checked out 20 books from the library and drove the fish store people crazy asking all types of questions when I first got the tank and when the goldfish got ich (we left on vacation and the food that the store people said would be fine for 7 days--a pyramid that disolved slowly and said it would feed a tank of 20 fish for 10 days--for my 4 fish (2 3 inch goldfish, 1 1 inch goldfish, and 1 weather loach, and 1 snail) was not enough. They got stressed, got ich and we came back on a Sat and the store didn't open until Mon, so even though I really tried, they all died, except the snail and the loach.) so I have done a lot of research, but most people and the store people say that real plants are not worth the hassle, but they look so inviting and the fish might like them better. Thanks for your help so far.
 
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