Persistent diatom algae issue

[flintcore]

I'm really struggling with this diatom algae in my tank, it's everywhere. I've got no silicates or nitrates, I'm providing plenty of bright light, but my sand has turned this awful browny-gold color. Every time I do a water change, it's back within 2 days. I'm at a loss, I've even got 5 sand sifting snails that should be helping to control it. I've noticed that in areas with no light, there's no diatom algae, but as soon as the sand is exposed to light, it's like a plague. Can anyone suggest what might be eating it, or what's going wrong?

[rusticore]

My tank's pretty old, I'd say over a year now. What's the deal with phosphate levels, should I be testing for that, could that be why I've got this diatom algae everywhere?

[flintcore]

Phosphate levels are zero. Tank is a year old, 12 months to be exact.

[rusticore]

I'm really struggling with this diatom algae in my tank, it's everywhere. I've got no silicates or nitrates, I'm providing plenty of bright light, but my sand has turned this awful browny-gold color. Every time I do a water change, it's back within 2 days. I'm at a loss, I've even got 5 sand sifting snails that should be helping to control it. I've noticed that in areas with no light, there's no diatom algae, but as soon as the sand is exposed to light, it's like a plague. Can anyone suggest what might be eating it, or what's going wrong?

I'm starting to think it's the test kits that are the issue here. Adding more flow around the sand area might help.

[felinxo]

I'm really sorry, I've gone and forgotten the size of your tank, but I'm thinking it might be down to not having enough cuc, as I said. Musho mentioned it, and I agree, your test kit might not be giving accurate readings - which ones are you using, and how old are they, by the way? It's possible that the algae is consuming the phosphate, making it seem like there's none, but in reality, it's just being eaten and then more algae is growing. Do you have any other types of algae in your tank? I'd be tempted to get my water checked at the lfs, just to be sure.

[flintcore]

My test kit's only a couple of months old, it's an API one. My tank's 190 litres and I've got plenty of flow, I'm just as stumped as you guys.

[rustyfox9]

I've had a similar experience with the API phosphate test, it's pretty unreliable in my opinion. I recall having a cyano outbreak and the API test kept showing 0, but then I switched to the Salifert phosphate test and my reading was actually over 1 - massive difference. This is likely because the phosphate is bound up in the algae and the live rock. Do you use a phosphate remover in your tank?

[rusticore]

I've gotta agree with the others, API phosphate tests aren't the most reliable. Salifert's a better bet, but you've got to be careful not to get one of their dodgy batches. ELOS is another good option, though I'm not sure if they're available in the UK yet. To be honest, none of these tests are as accurate as an electronic phosphate tester, but those things cost an arm and a leg. If you know someone with one of those fancy meters, it might be worth getting your levels checked out. Also, are you absolutely sure it's diatoms you're dealing with? It could be something way worse, like dinoflagellates.

[route4]

If you want a reliable phosphate test kit, consider investing in a D+D - it may be £30 but it's worth it for the accuracy.

[felinxo]

My tank's pretty old, I'd say over a year now. What's the deal with phosphate levels, should I be testing for that, could that be why I've got this diatom algae everywhere?

I'm cringing a bit at how blunt that came across.