Moving and replacing the sandbed?

[StrangeDejavu]

A little background info: Tank is a BioCube 29, been set up for 10 months now. Only inhabitants are a small Clown, Bangaii and a cleaner shrimp which get fed a small portion of LRS once a day. Early on in the tanks' life, I quarantine and treated a Tailspot Blenny. He looked ready to go in the DT, although still a little skinny. In May, I had to do a 3 day blackout for dinos. After unwrapping the tank, I couldn't find the little guy anywhere. I figured he was hiding well but after a few days of no sight, it was clear he had died and the CUC made quick work of him. I feel like this event is what caused the majority of my future algae problems. 2 months later (July), I come home from vacation and my tank is in meltdown mode. Spirulina cyano everywhere, bryopsis, hair algae all over the sand and dinos. My best guess is that a snail died the day after I left and caused that bloom since I had to throw one out. Since then, i've spent the last five months battling GHA from hell. It grows like a lawn on my sandbed and all over the rockwork. I've been hitting it hard with weekly gravel vacs, wet skimming, ROX carbon, Purigen, GFO and weekly 25% WC but I see little progress. The most noticeable change was when I began dosing Vibrant. Big results, but still not where I want it. I'm moving in a month and now i'm thinking the best thing I could do for this tank is throw the likely packed full of PO4 sandbed away and start with fresh sand at he new house.

Would I be risking an ammonia spike by doing this or am I better off reusing what I have now? I figure if I keep a cup of sand to seed the new sandbed, i'll at least have a head start on repopulating it with microfauna. Any opinions, or even better, stories of experience, are appreciated.

Here's a few pics, if they help. First pic is what my tank used to look like when it was doing well, and the following is what i've dealt with for months.

 

[saltyfilmfolks]

just toss it and get a new bag.
if you want to know how much po is in the sand put in tank water in a bucket over night and test the po in the morning.

 

[StrangeDejavu]

just toss it and get a new bag.
if you want to know how much po is in the sand put in tank water in a bucket over night and test the po in the morning.

That's a good idea, gonna do that next WC.

 

[john.m.cole3]

I wouldn't save a cup of your old sand. a 10 month old tank will house plenty of good bac in the rock's pore networks to keep the bio filter up while the new sand gets seeded.