Redfield Ratio

[eleodes]

hey y'all

there has been a good deal of back and forth about nutrient balance and it is very interesting. have you seen this?

http://www.xs4all.nl/~buddendo/aquarium/redfield_eng.htm

my system is looking pretty sad with declining macroalgae and some kind of red fuzz all over everything. here is a recent shot;

http://entomology.wisc.edu/~dbiggs/aquatics/2_june_05_tank4.jpg

i guess that a cyanobacteria bloom would be consistent with a NO3 deficiency and high phosphate. as per Samala's recomendation on a question about seaweed growth i got ahold of some Seachem Nitogen and added a dose this morning. it will be interesting to see what kind of response i might get.

 

[Samala]

Redfield ratio is a big topic.. I even treated it too simply on my website and am in the process of rewriting. For a great treatment of the topic, try http://aslo.org/meetings/carbon2001/karl/transcript3.html by the guys at Am. Soc of Limnology/Oceanography.

I notice that my seagrass tank mostly follows the redfield ratio of 16:1.. but this is not a static thing in the oceans, in some cases of N or P limitation it can shift.

Are you testing for nitrate and phosphate? Please test before you add more in! While we can certainly figure out some things by observation it cant hurt to double check your suspicion that your nitrate levels are too low. I'm also interested in the response you see.

>Sarah

 

[eleodes]

yes, NO3 has been at "0" ever since that tank cycled. unfortunately i still don't have phosphate test kit, but i hope to get one soon.

now (a little more than 24 hours later), i don't see change yet with seaweed, but i do notice that corallimorphs (which had also been looking sad) are much more fully expanded. i don't know if that might correlate with ^N(?).

 

[Samala]

Well, do the mushrooms get their nutrition from both photosyntehtic algae (zooxanthellae) in their host cells and what they eat? Or just one or the other? I'm not familiar with them. I imagine they exhibit a range of both feeding behaviors across the group.. where do yours fall in that spectrum?

Maybe if they are relying more on their symbiont algae for nutrition they are expanding in the increased N environment to let the algae cells get more light. ??

I've always wondered how a reef tank has thriving corals in a zero-N situation. No nitrogen seems to make me think their algae cells, which give them much of thier color, cant grow or at least not densely within the coral. Maybe Borneman would know..

>Sarah

 

[eleodes]

as i understand it, while they do feed, most corallimorphs rely heavily on photosynthesis. maybe that is part of the reason they tend to be easier to keep than most true corals. i think that it is the larger species that are able to actually catch careless fishes. some corallimorphs have tentacles, while others may use ciliary action to draw food particles to their mouths.

here is a thing that Julian Sprung wrote about mushrooms:

http://www.advancedaquarist.com/issues/oct2002/invert.htm

i believe that part of the reason that photsynthesizing invertebrates are able to make it in reef tanks despite very low N is due to use by the zooxanthellae of metabolic waste products from the animal cells. the original source of the nitrogen would have been the planktonic or dissolved food sources captured by the coral.

"0" NO3 readings on home test kits might also reflect a range of low levels in different tanks. the sump in my roommate's system is half full of bioballs and i bet those things produce some excess nitrate.

 

[eleodes]

well after putting in capfuls of Seachem Nitrogen for several days i am beginning to notice new growing tips on macroalgae. unfortunately, the cyanobacteria (or whatever the red fuzz is) also seems to be benefitting. the nitrate reading, however, has stayed at "0". i think that my substrate must suck it out real fast.

i was looking at another thread going back and forth about carbonate stripping from photosynthesis. interestingly, my pH has also gone down (quite a bit, to around 7.9) since introduction of KNO3. maybe that is why(?).

i added some more buffer to water.

 

[piercho]

Photosynthesis tends to drive pH higher, not lower. In a brightly lit eutrophic tank, daytime pH may range up toward 8.6 and higher.