Dying fish

Question
Hi, I have a fluval vicenza 180 tank, it currently is home to
4x zebra danio
2x neon tetra
4x frogs
1x clown plec
1x albino plec
2x male guppies
7x female guppies
2x algae eaters
1x male Siamese fighting fish
3x glass fish
2x shrimp

I have two live plants (not sure what they are) 5 artificial plants, a artificial rock set like a dome to provide cover and a pirate boat  with a tetra air pump. The filter is a external fluval 206, with a 200w elite heater. Ammonia 0, nitrate 50, nitrite 0, GH 500, KH 270 and ph 7.2, this was from a dip stick, which I know are not that reliable but also took a sample of water to lfs and came back ok. The tank was set up on 23rd may and was told could add fish straight away which I now know should of been cycled first. When the tank was first set up it had 13 neon tetra and 2 zebra danios, within 2 days all tetra had White spot and treated them with protocol whitespot and fungus, ended up losing 11 tetra and 1 danio, purchased 5 female guppies and 3 male guppies 2 weeks ago along with plecs, frogs and algae eaters within two weeks lost 4 female guppies and 1 male guppy. Do water change and gravel clean once a week approx 25%-40% depending how dirty gravel is. Feed them every other day in the morning on tetramin and sinking pellets. I don't understand why they keep dying, check levels of water regularly. I don't know what to look out for in terms of parasites, they don't give much indication that they are going to die, just seems to happen. The only thing I struggle to maintain is the temp it is currently running at 26 C and the heater is not plugged in as it takes it to over 30 c if it is changed the heater as thought there was a problem with it but new one still does the same.

If you have any suggestions on why my fish keep dying or any general advice it would be greatly appreciated, one more thing one algae eater seems to have small black lines running thru it, worms? if so how and what would I treat it with.

Thanks

Answer
Becki,
If I remember that tank is about 48 gallons. You have way too many fish. You have 4 algae eaters and that is about 3 too many. The lines are most likely on your clown pleco and that is normal, he should have them. You are correct that the tank should have been cycled before you added the fish. As for them dying, there could have been something wrong with them before you bought them. If you got them from the same store, try a different one. It can also be your Betta. Males should be left alone in their own 5 gallon tank. The Betta and the male guppy will most likely fight, and the Betta will probably win every time. You might want to remove him and put him in his own tank. When you bring home any new fish, always put them in your hospital tank for at least 4 weeks before adding them to the main tank. This way, if something is wrong with the fish, you might be able to catch it before it contaminates the other tank. With the tropical fish, you should have a heater that has a dial so that you can set the temperature. Those are the best ones to have. You nitrates are too high. It should be no higher than 20 ppm, and even lower with the clown pleco. I would suggest, if the other algae eaters are the common pleco, returning them to the store. Your tank is not big enough for them. The common pleco can get very large and will out grow the tank very quickly.