I just went through the EXACT same thing last week!! I've invested hours and hours in research and planning for our saltwater tank that I finally have cycling. Needless to say, I'm no longer interested in our freshwater tank which just like your case, mine also belongs to my 8 year old. So here's what you do...bribe him to take it down so you can replace it....with a Nerf gun wall!! Boom. Problem solved!! He's happier and so am I. One less tank to maintain and more focus towards saltwater