Alkalinity 300 and PH 8.4

Question
Hello,
   I am new to this forum and have a question that perhaps you can help me with?
I have a 30 gallon tank with 1 Swordtail (Male) and 7 baby (about an inch long now) Mollies or Platies ( don't know who the mother was). I had  a Dalmation Mollie (swordtail killed her, beat her up on her sides untill she lost color and she died) and an orange and black Platy (Swordtail killed her, ate her tail), I also have 2 Spirell Top Apple Snails, 5 Ghost Shrimp (one is carrying eggs) and a 5 inch Pleco. I have live plants in the tank as well.
   I have had this tank for over a year now. It started out with the Swordtail, which was a gift from a friend to my 3 year old in a tiny tank. I found a 30 gallon tank at a yard sale for 5$ and decided to get serious about having a nice aquarium. I have it in a place ( on the bar between the kitchen and living room, so it looks like a living window between the 2 rooms, very nice) where the temp is about 78 degrees fairly constantly.  It needs to stay there as it is the only place where it truly looks nice and is fairly safe from Dorian (my 3 year old).
  Lately I had noticed some tiny white worms (found out they were planaria) and so I did not feed the fish for 3 days but instead I would stir up the tank in one area or another and the worms would float around and the fish ate them, this made me happy after all I had read about them because I did not want to start putting all kinds of chemicals and what not in the tank, it must have worked because I cant seem to see them anymore. Oh, and I do a 25 water change once a week now in hopes of  getting the levels down and get rid of the decaying food that I have acquired when I was over feeding the fish to keep them full so they would not eat my fry as it was growing. They grew very fast by the way. My friend has had fry 5 months longer than I and hers are only half the size of mine so I feel like mine are thriving.
   My question is about the levels in the tank that show up on the test strip. Nitrate is 40, Nitrite is 0, Hardness 25, Chlorine 0, Alkalinity is 300 and the PH is 8.4.  According to the strip all are in the "safe" zone, except the last 2. I was reading articles about it and they said if I have any shells in the tank to take them out, I did this today so no more shells. Will that be enough to set my tank right? Or will I need to do something else?
Thank you in advance,
Jakkyn
P.S.  any advice on any of the other info I have in this post will be greatly appreciated. Also since my other fish are no more I would like to add some brightly colored Angel Fish to the tank, Dori Loves them when I show them to her on the web. Possible? What preparations do I need to make?

Answer
You want to do water changes that is all you really can do...without putting chemicals in your tank. PH should be down somewhere around 7.0-7.2 unless you put the product PH Down in which is a bit risky to play with because if you make it too low it's hard to get back up. Water changes should also help the alkalinity. I'm sorry it took so long to answer.