We did the daytrip to Laguna 69, which was offered by our hostel and operated by Solis for 50 /S per Person plus the entrance fee to the NP of 30 /S for one day. I will not describe the details of the hike as it was done before in other reviews e.g. by Fréderic.

However for me the weather in the middle of October was not very good. It was cloudy until noon when we reached the lagoon and up there it started hailing and raining. On the way back down it was a frequently changing mixture of rain and sunshine. Due to the clouds the views of the snow capped mountains were limited and also the colours of the lagoons were less bright than with light. Actually the most beautiful lagoon was the "female" lagoon of the Llanganucos were you pass by in the bus on the way to the trailhead of laguna 69 and normally a photostop is made. Despite my soaked rainclothes that were not so comfortable especially in combination with the cold atop at 4600m during the hail, also I had a bit of a headache even after two days in Huaraz at 3000m which made me take a pill against soroche. Even after doing so a headache remained for the rest of the day. I must say that I was not in the best mood and the weather in the beginning of the raining season was not good, but I think this treck couldn't impress me a lot after having done many dayhikes in El Chaltén and Fireland around Ushuaia.

I'm not an expert in Flora and Fauna but the whole set-up with walking through grassy valleys up to a glacier lagoon with some waterfalls along the way was pretty much the same. Of course it's impressive that here this kind of landscape is found 3000m than in the south of the continent. But in combination with the starting rain period it caused me to skip my original plan to do the 4 day Santa Cruz hike through a valley next to Laguna 69. It's a beautiful landscape nevertheless and many others of the group were impressed by it. In terms of the fauna our highlight was seeing some Vizcachas- rabbit-like animals with a bushy tail- at the rocks before the final ascent. Our binocular helped us watching the small mammals as if they were close even though it was hard to spot them in the grassy rocks with their fur colour. I disliked a lot the many cows and there omnipresent excrements. I don't know if their grazing and shitting has a negative impact on the environment here, but I'm sure they're not part of the protected wildlife and therefore shouldn't be here.  
 
When you visit Chavin from Huaraz you cross a mountain pass that is also part of the NP. You can see laguna Querococha on this ride. 
 
We did also a daytour to the glaciar Postoruri similar to how Frédéric described it. Our hostel booked us into a Turismo Romero tour which I can NOT recommend. If you´re a typical Peruvian tourist you would have probably liked it, but for western tourists (we were 5 young people from India living in Europe, Canada, USA and us) it was not a good tour. The focus was more on a comfy day with loads of eating and drinking rather than visiting the NP. The first and last stop was eating and drinking in a restaurant on the way in Ticapampa. Additionally we assume that the guide Alex had a deal with the NP guard to embezzle our entry money to the park and put parts of it in his own pocket. Anyhow the places we visited are beautiful. I especially liked the Puya Raymondii, the huge bromelia plants that are standing in the tundra like landscape in different consitions. Some are already dead, some have their main flower part up which is really big and some are in the state of waiting to bloom one day. Also we visited a lagoon with nice colours and a cold water spring that is rising water up to the ground constantly and that our "fun" guide couldn´t explain chemically. The glaciar itself lies at 5000 meters above the sea level and it´s quite breathtaking physically to walk to ist feed. It takes about 30 minutes. There are also some fossils that can be found close to the glaciar remaining in the rock from ancient times. 
 
Parque Nacional Huascaran is a beautiful national park that reminded me a lot of different places in Patagonia and Fireland I had visited before. Probably flora and fauna are different but the principle of glaciars, lagoons, rivers and tundra landscape are similar. It feels like a similar landscape lifted up 3000 meters and pushed to the equator. I expected to be a bit more positively shocked by its beauty though but the other travellers were so it´s probably more about me and not the nice landscape.