...i know my tank has been cycled when amonia is 0 and nitrites are 0 right?
Not necessarily.
Let's say you filled up a tank with salt water and sand, added nothing else, and let it sit for a month. All during that time, and at the end, your ammonia and nitrites would read zero. But that doesn't mean your tank cycled. It didn't cycle because you needed a source of ammonia to feed the bacteria that will cause the cycle.
This is why I keep asking what you used as an ammonia source.
If you used rock from an established tank, and the rock was kept damp during that 1.5 hours out of the tank, then you most likely brought over a fair amount of bacteria with it - the bacteria that will convert the ammonia to nitrites, and the nitrites to nitrates.
BUT... that bacteria will only stay alive if it has ammonia to "eat". And without an ammonia source, over the course of a month the bacteria could've died off, leaving you back at step 1... no beneficial bacteria in the tank and having to cycle the tank.
That's why the suggestion has been made to add something - fish food, a cocktail shrimp - something, to basically rot in your tank and "test" to see if those bacteria are alive and well. If they're not, then you'll see ammonia show up. If they are, then you won't see the ammonia and instead you'll see an increase in nitrates.
You're thinking along the same lines that I've been thinking...
I personally belive the nitrates have been there since day one when i got the LR from a mature tank.
Have you tested your RO/DI for nitates? Since you're reading phosphates in your RO/DI output, either the test kit is wrong, or your RO/DI unit is buggered up. 0.5ppm phosphates is incredibly high, even assuming your DI resin is depleted and you're just getting the filtration from the RO part of the unit. Pardon the dumb question, but are you sure your RO/DI unit is plumbed correctly, and you're not accidentally putting the "pure" water down the drain? There's been many a person here guilty of that!
In a nutshell... if you're doing a 40% water change, and seeing no change in your nitrates, you've got two choices - your test kit is wrong, or your source water has nitrates in it.
Regarding the cycling issue, hopefully with my rather long-winded comments above, you can see where I'm coming from with wondering if you're really cycled or not. I'd just hate to see you posting in a month when you're trying to deal with an ammonia spike after you added your first fish.
The algae... is it a brownish dust? Or is it slimy red?
