Originally Posted by Mebbid
Pb : I would agree with you completely except for the fact that theres no ammonia. Theres too much decomposing biological matter in the tank creating the huge nitrate spike. The bio balls have nothing to do with decreasing the nitrate levels so thay doesnt really make sense either.
My best thought at rhe nutrient source atm is the sand. Where did you get the sand from that you put in your refugium?
sorry Mebbid, but your incorrect.
If the OP is suddenly noticing elevated nitrate levels AFTER replacing the bio media in the sump, the only logical assumption to make is that days earlier there were corresponding spikes in ammonia and nitrite respectively.
Her testing zero ammonia & nitrite NOW tells us nothing about what it was last week, BUT the elevated and climbing nitrate levels do.
That is also the ONLY reason I advise against cleaning the canister at this time, it would possibly make matters worse.
Her system, if the live rocks pictured are the only bio-media in the sump, is very, very under filtered in regards to biological bacteria and the available surface area for it to colonize. The bio-balls, no matter how inefficient, provided much more surface area than the rock in there now.
True, by virtue of their design, bio-balls don't afford much in the way of de-nitrification, but their removal I guarantee is the primary source for this upheaval.
It is that decrease in available surface area in the filter sump that is/will give her issues until a better bio-media is employed and the colonies are allowed to get back up to full strength.
remove/reduce biological filtering capacity=
spikes in ammonia then nitrite=
death and disintegration of corals/inverts=
even more ammonia being produced=
increasing nitrate levels=
more stress and dying corals=
ever worsening water quality
I don't know, the cause and effect progression seems pretty clear to me.