Marco (Base) Rock & Denitrification

[Tuna Melt]

Those of you using Marco Rock (and especially those using Marco Base Rock). What are your nitrate levels?

I have 1-3 PPM nitrate and .07 phosphate. I have denitrification going on somewhere in my tank. My nitrates have been at that level for ~9 months except for a three week period following an in tank Cipro treatment after which nitrates spiked to 20. I believe the Cipro decimated the population of denitrifying bacteria hence the spike. My tank is loaded with fish and I feed heavy (1.75 cubes of mysis a day to a 30 gallon tank). I’ve been feeding almost exclusively mysis which has the highest N/P ratio of any common food we feed to our tanks. All this leads me to believe I have denitrification going on. I don’t think it’s in my 1-2 inch sand bed since I disturb it often and have slowly been syphoning it out (targeting a .75” depth) to rule that out. That basically leaves me with the rocks. 100% Marco Rock. The top suspect are these Marco base rocks I have that are mostly submerged in the sand. I have two medium peices in my ~30 gallon tank. I’d be curious to know if others that have these have similarly depressed nitrate levels.

https://www.bulkreefsupply.com/medi...sa_mt=&hsa_net=adwords&hsa_ver=3&gad_source=1

 

[doubleshot00]

Corals are probably absorbing it.

 

[twentyleagues]

So many variables. I am sure its possible. I have marco base rocks, fuge full of different algaes, 3" sand bed in fuge, 1.5-2" sand bed in display. I still do weekly 10-20% water changes to keep my nitrates around 10-15ppm.