Water change? Yes/No... Lesser of two evils

[mwladdicted]

So here's my dilema... I have an SPS reef. I've always sworn by weekly small water changes. My problem with my current system is that every time I do a water change, I bottom out my NO3, then my PO4 skyrockets (Redfield Ratio), ruining my hard worked sps colors. I feed heavy, cut skimmer and change my media and start over. So my question is, play by the book and do my water changes or just let it be with no water changes. My NO3 sits at 2ppm without water change and my PO4 stays around .05ppm. I feed very heavy. My water changes are ~ 7% on a 60 gallon system. Thoughts??? Cost/benefit for both options??

Thanks!!

 

[Sabellafella]

I thought i was crazy, i had that issue for like 6 months ,(reef was 6 years old) so i didnt really pay that much attention, i started doing water changes bi weekly and monthly nd started carbon dosing with gac nd skimming

 

[sswsanjay]

Same problem, what I started to do to solve this issue was everytime I mixed fresh water for a water change I added some calcium nitrate, some people use potassium nitrate. I like to keep my reef around 4ppm nitrate so by bumping up my water change water to this 4ppm nitrate by dosing it, it doesn't change my main tank. But I still get the benefits of adding trace elements and all the other benefits of small water changes! My SPS seem to be loving this and my phosphate doesn't fluctuate doing it this way.

 

[Sabellafella]

Yea i started dosing the kn03 but it would drive my p03 nd p04 would show zero on hannah checkers was driving me crazy, best simplest advice is to change your water exchange to bi weekly

 

[mwladdicted]

Yeh I try to keep things simple and I'd rather not start dosing something else.. So you suggest waiting longer is going to make a difference even though it hasn't budged from 2ppm after a month? I guess i should have mentioned that at this point I'm trying the no water change option lol. The old routine is just screaming do a water change at me and im not sure if i should or not lol. I haven't done a water change in a month now...I mean I guess I could just start doing 1 gallon WC's.. seems pointless though

 

[Randy Holmes-Farley]

FWIW, I'm not understanding why small water changes would bottom out nitrate and cause phosphate to rise.

A 10% change ought to only drop nitrate from 1 ppm to 0.9 ppm.

How big of changes are we talking about?

 

[mwladdicted]

Hi Randy,

5 gallons in a 60 gallon system. It's happened multiple times now... my nitrates hit zero, then my gfo becomes ineffective and my po4 goes up. As soon as I start feeding heavy again and cut out skimmer it returns to what I said earlier. My main question is am I doing more damage to the overall health of the reef by not doing a water change keeping things stable or by not giving the refreshing boost of new water throwing nutrients levels out of whack?

 

[Randy Holmes-Farley]

Well, I'm not sure what is happening, but low (or no) nitrate doesn't make GFO ineffective. Nitrate has no effect on GFO. Maybe it is just getting depleted.

Are you using tap water to make the salt?

In general, small water changes are not a direct cause of nutrient in stability.

Water changes can supply depleted trace elements that might be limiting how well macroalgae or other organisms can grow. Iron, for example, gets depleted. So the water change may boost nutrient export in that way and cause nitrate and phosphate to decline more rapidly.

 

[Oceansize]

I thought i was crazy, i had that issue for like 6 months ,(reef was 6 years old) so i didnt really pay that much attention, i started doing water changes bi weekly and monthly nd started carbon dosing with gac nd skimming

I may be an idiot, but I've always gotten the impression that running GAC and dosing carbon are not the same thing and do not serve the same purpose. GAC removes DOCs and dosing carbon (vodka, vinegar) is a denitrifier. Am I mistaken?

 

[Randy Holmes-Farley]

I may be an idiot, but I've always gotten the impression that running GAC and dosing carbon are not the same thing and do not serve the same purpose. GAC removes DOCs and dosing carbon (vodka, vinegar) is a denitrifier. Am I mistaken?

Maybe he means he does both. I do both.

 

[Oceansize]

Maybe he means he does both. I do both.

Then it was worded confusingly. "I started...carbon dosing with GAC and skimming"...it's hard to discern whether he considers the GAC to be carbon dosing.

 

[Jdmonealp]

What kind of salt are you using?

If the salt happens to have a carbon source in it, it is possible that theres a bacteria bloom, then it takes nitrate down to 0... just a theory.

 

[Sabellafella]

I may be an idiot, but I've always gotten the impression that running GAC and dosing carbon are not the same thing and do not serve the same purpose. GAC removes DOCs and dosing carbon (vodka, vinegar) is a denitrifier. Am I mistaken?

Lololol there not the same , i always run gac nd did dose racing fuel as a carbon additive but switched to nopox

 

[Sabellafella]

[HASHTAG]#mwladdicted[/HASHTAG] what 2 part do you use (if one) or do you use a cal reactor?

 

[mwladdicted]

Low NO3 has habitually made my GFO ineffective. I test consistently with red sea test kits that are not expired. If my phosphates are up I can almost guarantee my NO3 is zero. Yes, I use RODI in my SPS tank. If i didn't i'd say my nitrates probably wouldn't be zero. I do vacuum my sand tho...I understand that WC's "replenish trace elements". which is why I'm weighing the cost benefit analysis on to or not to WC. If i understand your last paragraph correctly Randy you're saying that the replenishing of trace elements is fueling the growth of macros(my fuge for example), boosting their uptake of nutrients due to the surplus of new food conjunctively taking my "nutrients" with them?

To answer the next question, I use red sea coral pro salt

@Sabellafella, I dose B-Ionic with my doser along with Kalk

Here is a link to my build for equip questions:

https://www.reef2reef.com/threads/mwladdicteds-50g-cad-upgrade.216689/

Note: My tank is not under any duress, for now... which is why I am asking the question.

Last test:

DKH - 8.0
Ca - 440
Mg - 1350
PO4 - 0.05
NO3 - 2ppm
SG - 1.024

Thanks For all the help guys!!

 

[Sabellafella]

I use esv b ionic also ,the 2 part has alot of trace elements, ive ben using bionic in conjuction with triton testing , i use rs coral pro bi weekly and in my 200 i do a 50 gal change every 3 months with esv , only difference with triton is more K is supplemented in rscp. .. so trace elements you should be fine, on another note your water changes bring your nitrate values below phosphate , witch via redfield ratio cant process the phosphate correctly causing cyano( in my case) , will make you seem like your gfo isnt effective

 

[Randy Holmes-Farley]

Low NO3 has habitually made my GFO ineffective.!

Again, that is just not possible. There's no mechanism for low nitrate to impact whether GFO is working or how well. Something else must explain what you are observing.

 

[Randy Holmes-Farley]

, on another note your water changes bring your nitrate values below phosphate , witch via redfield ratio cant process the phosphate correctly causing cyano( in my case) , will make you seem like your gfo isnt effective

How does that make phosphate rise? Growing cyanobacteria will need phosphate.

 

[Sabellafella]

Im not really sure lol but ive had this same issue so many times, as soon as nitrate falls below phosphate, the po4 skyrockers and cyano it is ( for me) =) but yea the gfo seems to not work at all, it seems strange but it does happen

 

[Lenny_S]

This is strange and doesn't really add up. GFO being a binder is not dependent on anything but its saturation point. So the more likely answer is that at the time of the WC the GFO is saturated and not absorbing phosphate, coupled with the lack of nitrate even the amount of phosphate used in the redfield ratio is not exported. So phosphate rises... It's the only logical explanation.