And thank you for the answer, I'm taking it you may be a leading if not the leading voice on chemistry/parameters
I mean, he has his own chemistry forum here for a reason. =)
I don't think everyone always agrees with Randy on everything, but you should always pay attention to what he says. He knows what he's talking about. =)
Remove your phosguard and test daily to see how your phosphates move. You can definitely survive higher phosphates, but if the phosguard is keeping phosphate growth in check you may need to find another way to fine-tune your removal to keep your phosphates at ideal levels. Rowaphos is a good alternative here, especially if you're using a canister filter as opposed to sumps and reactors.
With regards to your sand - hard to see from the picture, but the spots kind of look like dinos to me, which often take hold when your nitrates/phosphates are low. If you want clean sand, I'd recommend three things:
First, get your phosphates up a bit and see how those spots on your sand progress. Wait and see, basically.
Second, you can get a bit more flow around the sand bed, but that's a tricky thing to get right. Too much flow and you can over-agitate the sand, leading to sand mountains and (depending on how long your tank has been running) the release of nasty chemicals like hydrogen sulfide. So if you do this, go slow and adjust a little bit at a time.
Third, get in some livestock that will churn up your sand bed a little. Conches are great at this. Sand-sifting gobies are good, sometimes too good. Hermits and emerald crabs, also good. Nassarius snails also do this a little bit, but not as well as you might think.
Finally, over time your sandbed is likely to be colonized by all manner of microfauna. Once these get established, they basically keep the sandbed clean better than anything else.
