If it contains added slow release fertilisers it doesn't seem to organic. Might be a bit acidic as well, you want to try and avoid peat.
I've used the Brunnings one though, it was good if I remember correctly, I would go for that, maybe mix it with some sand because if I rememebr correctly it smelt strongly off manure, I mixed mine with zeolite. Or that may have been a different brand, if it doesn't smell of manure ignore that advice lol. Remember to mix in some crushed marble or shell grit to stop it going sour.
That sand looks really good in a tank, don't go to deep though, may 2cm with the sand.