Hi bayo.
ok so you are in a fish in cycle. this isnt the best way to do it tbh especially with neon tetras as they are quite a sensitive fish when it comes to poor water quality which you will have during a fish in cycle im affraid, but you were unaware of this so its not your fault.
there is much debate about the bacteria in a bottle with most people saying that its a waste of time and money as the bacteria that was in the bottle has nothing to survive on while its being stored so therefor dies off before you have even opened the bottle. now you have it you may as well use it but i would be suprised if it helped the cycle at all....
so you have had the tank set up for 2 weeks and the neons are still alive so thats a good start. your pH is fine nothing to worry about there just keep an eye on it during the cycle as it can drop which may cause the cycle to stall, so test it often and keep an eye on it. the 0 ammonia is great as ammonia is toxic to all fish so no worries here. with nitrite at 5ppm it shows that you have the bacteria formed that converts the ammonia into nitrite. nitrite is also toxic to fish though so this level isnt good for them, it needs to be at 0 ideally. the only way to get it down to 0 is to do water changes during the cycle which will reduce the nitrite level. a 50% water change will half the amount so calculate the amount of water that needs to be changed each time to get it back to 0. this will probably mean water changes every day until the filter is cycled...
have you tested your tap water for nitrate at all? if not then i would do so. my tap water has 10ppm nitrate. nitrate is the end product in the cycle and this will continue to rise as the nitrite is transformed into nitrate, its ok to have levels of nitrate in the tank as this doesnt seem to effect many fish until its starting to get quite high. once the filter has completed its cycle and you have 0 ammonia and 0 nitrite constantly the nitrate will rise as i said. live plants can help remove nitrates from the water as they use them to grow along with other things. you will read about people doing regular water changes in a cycled tank and this is mainly to reduce the nitrate levels in the water and to add minerals in the tap water that will help the fish keep healthy. testing your tap water will let you know the nitrate levels you have before the cycle is complete, once it starts to rise over this tap level you know that the bacteria that transforms the nitrite into nitrate is forming.
in time your results should be ammonia = 0, nitrite = 0, nitrate = more than your tap water
for the time being keep testing the water for all the above including the pH and do relevant water changes to keep the levels at 0 for ammonia and nitrite.
i would reccomend doing a large water change today of about 80%. leave it for an hour or so then test it again. you will still have nitrites but much less and do another change that will hopefully get the level down to 0. apart from the fishes health this is the bad thing about doing a fish in cycle as you need to change lots of water and you will get through plenty of dechlorinator during the process. the reason shops tell you to do it this way is because fish that die during the cycle will need replacing and along with plenty of dechlorinator and bacteria in a bottle products they sell you make them a nice sale
stick at it and the maintenance becomes a water change once a week instead of once or twice a day and on a tank of your size will take you 10 minutes to do so you can enjoy the tank instead of finding it a right mission to keep on top of. there is light at the end of the tunnel.....
also what water test are you using? the reason i ask is that there are paper strip tests available that are cheaper to buy but much less accurate than the more expensive liquid test kits. look on ebay for an API freshwater master test kit and this will have everythig you need and will last a long time and are much cheaper on ebay than in the shops
good luck with the cycle and keep at it.
