Im comfused by your comment "it looks to be cycled, BUT IT STILL HAS AMMOMIA". The only way to see if a tank is cycled is if the waste produced by your tank results in no detectable ammonia and nitrite. You are seeing ammonia so your tank isnt cycled. What is making you say it looks to be cycled? It isnt, you are seeing ammonia.
Couple of things can be happening. Either you somehow crashed your cycle and you need to recycle the tank or there is a new ammonia source and your cycle needs to catch up.
Im not sure what the purpose of methylene blue was. It wont do anything to help with ammonia issues, and it can kill the beneficial bacteria responsible for your cycle. Could you explain more about why you used this? This could be why you are having trouble re-establishing your cycle.
As to what caused the ammonia in the first place. A few possibilities.
- Over cleaning the filtration system.
- The fish have grown, increased the bioload, your filtration is no longer sufficient.
- Something died and you didnt notice.
- Maybe your source water has changed. Maybe the water treatment went from chlorine to chloramine which would be a be new ammonia source. Have you tested your source water?
- Maybe your water company was doing work on the system and added additional treatment to the water at the end of works. You do a water change and your normal water conditioner isnt sufficient and the chlorine/chloramine killed off your cycle.
Whatever happened was so long ago now, we probably will never be able to discover what it was. But we know either your tank lost its cycle, or it needs to catch up due to increased ammonia from somewhere. I would stop with the medication, that wont be helping and could be causing your ongoing inability to re-establish your cycle. I would try dosing a beneficial bacteria product like Dr Tims One and Only or Tetra Safestart, that may help. If you know someone with fish and an established tank, getting some media from an established filter and adding it into your filter will speed up this recycling process.