Nutrients keep climbing despite carbon dosing

[JonasRoman]

Hey all,

I've posted a couple of weeks ago about my nutrients continually climbing. I thought I won't do anything crazy with it so I just started dosing aquaforest's bacteria and carbon source to feed heterotrophic bacteria and help bring nutrients down naturally. I'm currently at the highest recommend dose and the nutrients keep climbing regardless.

My tank is 500 liters total, I have a roller mat, octo regal 200 int skimmer and do 15-20% water change every 2 weeks. Here's a record of my parameters from the last 3 months. The tank is obviously young at barely 5 months but the corals aren't happy, I lost almost all SPS that were already growing and I'm at my wits end.

I have the following fish:

Hippo Tang
2x ctenocheatus tangs
Foxface
2 clownfish
Longnose butterfly
And like 3 other small fish (think chromis or goby)

I feel a pinch or 2 dry food and up to 4 cubes frozen, plus some nori.

The problem with carbon is that it needs area, and preferably enough with anaerobic zoones to work properly. To rely only on heterotrofic assimilation in water column, and the believe all that will be remived by skimmer, will not work, and is the reason I believe of your issue. This scenario is especially common in bare bottom tanks that due to that lack a lot of beneficial area for the bacteria. Second, the Po4 is sky high so I would try to brung that down with selective binding agents, to make it more easy for subsequent bacteria to do the rest of the job. So I would do this 1) Make sure you have sand in tank, at least 5 cm. 2) install a few anareobic blocks from Maxspext, those specialised for denitrification. 3) Install AF biostones. Those will be a good area for both assimilation but later also denitrification as the Maxspext. 4) Bring down Po4 with GFO to 0.15, then stop and the biology do the rest.

Jonas