Can’t reduce Nitrates and Phosphates

[chaser]

I am a bit confused. After finding out I had high nitrates and phosphates a week ago I promptly did a 50% water change and began running carbon and GFO in my filter. It’s only been a week but I’m disappointed as my nitrates have only gone from 158 to 135. And my phosphate number actually increases from 2.6 to 2.7.

My tank is about a year and a half old. My main purpose in getting these numbers down is to get better growth out of my coral as the coral I have hasn’t been growing much.

What am I missing? I thought with such a large water change that my numbers would be significantly reduced and I’m not sure how long the carbon and GFO take to make a difference.

All other numbers are great. I feed once per day but would say I feed heavily as I want my tangs to be fat and healthy. I have a lot of clean up crew for the extra food. Any suggestions would be appreciated.

 

[Tangdora]

A fifty percent water change assuming you are using rodi will only reduce your nitrates by 50% and that is only same day if you were to test again. If you’re testing a week later and expecting to see a drop but are not then your nutrient import is exceeding your export. Several questions here.

1) Tanks size
2) How many fish
3) What is your current export method outside of WC. Skimmers, turf scrubber, carbon dosing ets. Also what size is the equipment.
4) what are you feeding.
5) do you have any current algae problem. How intense are you running your lights. Specifically your whites.

 

[Isaac Alves]

I think we need more details about the tank and filtration. Also, pictures of your system will help.

• What test kit are you using?
• what size is the tank
• what is the bio load
• GFO and carbon will not affect Nitrates (outside of housing some bacteria)
• GFO, is most efficient in a reactor, with controlled flow to have a slight tumble
• Do you a have a sand bed?
• Those numbers after a water change seem reasonable to me
  
  

 

[chaser]

I think we need more details about the tank and filtration. Also, pictures of your system will help.

• What test kit are you using?
• what size is the tank
• what is the bio load
• GFO and carbon will not affect Nitrates (outside of housing some bacteria)
• GFO, is most efficient in a reactor, with controlled flow to have a slight tumble
• Do you a have a sand bed?
• Those numbers after a water change seem reasonable to me

Thanks for responding. Small setup right now. 30 gallon tank with 2 HOB filters, each filter was it can handle up to 50G. One filter has media and a carbon filter floss bag in it and the other filter has only GFO in it (Fluval Clearmax).

I do have a significant bioload. 2 juvenile tangs, 1 clownfish, 1 mandarin, 1 watchman goby, and 1 lawnmower blenny. 1 anemone CUC includes a mix of 20ish hermit crabs/ snails and 2 turbo snails.

My substrate is arogonite with about 30lbs of live rock. The test numbers are from my LFS. He uses the Spin Touch FF.

 

[chaser]

A fifty percent water change assuming you are using rodi will only reduce your nitrates by 50% and that is only same day if you were to test again. If you’re testing a week later and expecting to see a drop but are not then your nutrient import is exceeding your export. Several questions here.

1) Tanks size
2) How many fish
3) What is your current export method outside of WC. Skimmers, turf scrubber, carbon dosing ets. Also what size is the equipment.
4) what are you feeding.
5) do you have any current algae problem. How intense are you running your lights. Specifically your whites.

I answered below but to answer your questions also, yes I run my white lights at 100% percent for 10 hrs per day. No algae problems. I feed a mix of pellets/ flake and frozen food once per day

 

[Isaac Alves]

You gotta get your own test kits so you can build a trend and test weekly. If you got the cash pick up the Hanna Nitrate and Hanna ULR Phosphorous testers (or the phosphate one but I think the ULR versions is more accurate (?)), otherwise, a trusted test kit like Salifert works.

Weekly large water changes will help with nitrate.

You do have big poopers in there for sure.

 

[Mr. Mojo Rising]

What test kit are you using? The ones I’m aware of dont measure that high.

 

[Randy Holmes-Farley Verified Community Expert]

What am I missing? I thought with such a large water change that my numbers would be significantly reduced and I’m not sure how long the carbon and GFO take to make a difference.

Water changes are not a good way to reduce phosphate since there is a large fraction of the total phosphate bound to rock and sand, and when you try to reduce it, some of that comes off again.

Nitrate should respond exactly to water changes, with a 20% change lowering nitrate by 20%.

 

[mcarroll]

I am a bit confused. After finding out I had high nitrates and phosphates a week ago I promptly did a 50% water change and began running carbon and GFO in my filter. It’s only been a week but I’m disappointed as my nitrates have only gone from 158 to 135. And my phosphate number actually increases from 2.6 to 2.7.

My tank is about a year and a half old. My main purpose in getting these numbers down is to get better growth out of my coral as the coral I have hasn’t been growing much.

What am I missing? I thought with such a large water change that my numbers would be significantly reduced and I’m not sure how long the carbon and GFO take to make a difference.

All other numbers are great. I feed once per day but would say I feed heavily as I want my tangs to be fat and healthy. I have a lot of clean up crew for the extra food. Any suggestions would be appreciated.

I agree that you will want to double check those numbers....all of them sound VERY high, even according to "high" standards.

Especially for a tank that's just over a year old. How are you feeding and what foods are you feeding?

What is your standard for "coral not growing much"? (Slow growth is the healthiest, BTW.)

I agree that you are missing something (see Randy's comment about nitrate), but not sure what yet.

IMO stop using all the extra filtration (this can tweak your corals) and instead figure out what drove nutrient levels up so high. (Assuming your numbers are validated as correct.)

IMO it has to be something like over feeding or broadcast feeding where there is LOTS OF FOOD WASTE. This will allow A LOT more of the N and P in the food to end up in the water vs if the food is eaten and digested first.