My spring is very cold 55 degeres in august and july and the pond has trees all around it so its got plenty shade. plus i recorded that low flow rate only one time this summer. my max flow was 35gpm.so i respectfully disagree but i will keep an eye on that this summer.Now the GBH might be a big problem though the sides of the pond are very steep as you see in the pic if they do become a problem what do you recomend to dispatch or deture these pests from stealing my fish. keep in mind money is a huge issue consideriding I am a teen and dont make a lot of money.