Thanks for your quick replies and reminder to test all parameters:
pH 8.3
PO4 0.1
Ca 400
Mg 1200
Nitrate 0 (since Phosphate is high, might check this to confirm)
Nitrite 0 ((API)
Ammonia 0
Alkalinity 9.3
Salinity (refractomer)
All others are Salifert and am planning to buy some Hanna checkers.
I have always had uncertainty about how test parameters relate to or effected by the biological activity in the tank. If parameters look good, what else can explain what I am seeing? Along with more clean-up crew, would GFO be a good addition? Could GFO be added to the chamber after the skimmer?
Long winded response to follow.
My answers below are assuming you are going to add corals/other inverts (beside the CUC) sooner rather than later
Overall, I think you're doing a great job. Even those of us who have been in the hobby a long time (I've been in over 40 years) deal with algae issues from time to time. Just two years ago, I had the worst outbreak of cyano I've ever had. If you're curious about all the things I tried, here's the
thread on that battle. It was not fun.
Your ammonia, nitrite, alkalinity, pH and calcium all look good. Magnesium and nitrate are a bit low. As mentioned before, phosphate is a bit high.
Alkalinity is just a tad low, I personally shoot for 10 and generally keep my magnesium at 1300.
Phosphate should be in the 0.01 - 0.03 ppm range. You can lower phosphate by putting GFO in either a
media bag in the sump or set up a
media reactor. The media reactors are much more effective than just putting the GFO is a bag in the sump as they force the water through the GFO.
We no longer try to achieve zero nitrate for reef tanks. The recommended reading is 1-10 ppm. I actually add about 2ml of
nitrate daily to my 40 gallon tank to maintain those levels. But, I would double check your nitrate levels with a different test kit before adding nitrate to the tank in case your test kit is bad.
While I think you have diatoms, I'm not 100% certain.
@kharmaguru @Reefing102 any thoughts here?
If it is diatoms, here's a great
article by
@ReefBum on how to eliminate and prevent diatoms. From the article, "
Diatoms feed mainly off of silicates but also consume dissolved organic compounds, phosphate and nitrates."
Do you test the TDS of your post RODI water? If so, what is the reading? If zero, we can assume silicates are not the issue. So, it must be either the nitrates and/or phosphates. You could be showing zero nitrates because the diatoms are consuming it.
Disclaimer: There is no single correct way to successfully keep a reef/marine tank. What may work perfectly for one person may by an utter failure for another.
That said, here is what I would do. Weekly water changes in the 10-20% range siphoning out as much of the diatoms when doing so. Add GFO either via a media bag or reactor. Be patient, nothing good happens fast in this hobby.