Can you clarify what you mean by eutrophication, and why it's a negative? In my studies, I've only seen eutrophication used to refer to a situation where excessive levels of nutrients build up in the water, leading to an explosion of simple primary productive organisms (such as algae) that end up crashing and decomposing, robbing the system of oxygen.
Given your statement about biodiversity being indicative of eutrophication, I have a feeling that you're talking about another use of the word that I'm not familiar with. I'm kinda new to this forum, so forgive me if that's a dumb question.
eutrophication is just the build up of nutrients, mainly phosphates and nitrates. they can be in both organic and inorganic forms. we are just able to test for inorganic phosphates. all living organisms contain phosphates. if there is total increase in the total biomass of the system, then the system as a whole is becoming more eutrophic. as long as the biomass that is increasing is what we want (say corals and the fish growing), then we can control the total amount of eutrophication in the system. when the biomass is increasing because of "biodiversity", then there is a definite increase in total nutrients in the system. all organisms produce waste. waste contains nitrates and phosphates. unless this waste is removed it just adds to the total mass of nutrients in the system. if we are always adding food, then the exports must equal the exports in order to maintain the trophic level of the system, minus the amount of nutrients needed for growth i the biomass of the organisms we are wanting to keep.
Reefin' Dude,
I was just reading through this thread and wanted to post, since I felt compelled to do so. I'm wondering where you have gotten some of this information that you are speaking of?
i will start posting references as we go along.
The microflora and fauna that "has to eat something" usually eats what fish don't eat, or have eaten. That detritus is recycled into worm poop. After worms have their hay-day, the size of this detritus is small enough to end up in the sandbed and deep within live rocks where anaerobic bacteria (Nitrobacter and Nitrosomonas) decompose it even further into hydrogen sulfide and nitrogen gas. large pockets of hydrogen sulfide is something to avoid - which is why many long term "in display" deep sand beds don't work. Nitrogen gas is harmless and is released from the water without a problem. Nitrates and phosphates ... either organic, or inorganic are used by algaes and regularly harvested from the aquarium. Skimmers, however, skim out the dissolved organic compounds before they can be broken down into nitrate and phosphates.
the problem is that algae is also leaky. it releases up to 40% of the inorganic phosphates it takes in the form of organic phosphates.
Algae under the hood link.
it doesn't matter how small the poo becomes, if it contains P, then it has to be exported physically, it can not be off gassed. if algae is growing, then that means that there is enough inorganic nutrients for it to feed on. if exporting algae was capable of reducing the trophic level of a system, then eventually the algae exported would die off because it has run out of nutrients.
the siphon and the skimmer are the best weapons we have against phosphates. here is a graphic showing what the different methods of nutrient control we like to use and what parts of the phosphate cycle the address.
Also, you mentioned about pH swings that you say are caused by the breakdown of dissolved organic compounds - but I know this for a fact is incorrect. Like I said, I would like to know where you have gotten your information. pH is dictated by two things. The first being the alkalinity - which is the measure of the resistance to the change in pH. It's important to keep alkalinity high. The second is that CO2 in the water column actually creates an acid, called carbonic acid (you probably drink it every day), which lowers the pH of the water.
the bacteria that break down organic material release CO2 as a by product. suppressing the pH of the system. we are talking about basic decomposition here. carbon dioxide is a by product of decomposition.
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Let me see... what's something that regularly uses CO2 to make glucose? Ah, that's right! Algae! So, by having a fully functioning refugium, you are creating a more stable pH by having something to uptake CO2 and release beneficial O2 into the water. As one of my favorite Breaking Bad actors would say... ding ding ding ding! lol. Algae also needs phosphate in order to make DNA - to make new tissues. So,... wait a minute.... Algae not only can stabilize pH by decreasing CO2 in the water column but it also removes both inorganic and organic nitrate and phosphate and ammonia before bacteria get a hold of it??! WOW!
but why do you need to stabilze the pH in the water? why is the CO2 there in the first place? you are trying to correct a problem that is not there if the wastes being decomposed were removed before they start decomposing and producing CO2.
Your only good point that you have made is that we should all occasionally "hurricane" our tanks by cleaning out as much built up detritus as we can, just like mother nature would do on her own. As far as using refugiums and algae as part of a filtration system - I see no detriment other then a possible lack of yearly maintenance and a lazy reefer.
the detriment being that if the system is designed to be ULNS and a live sump (hobby refugium) is incorporated and is able to grow algae, than this indicates that the system is not ULNS. the algae is a biomarker.
Corals - even SPS corals need some organic and inorganic nitrates and phosphates to live and thrive. Phosphate is what organisms use to create new DNA... because what is DNA made of? Sugar, phosphate and nitrogenous bases/dimers. Limit these systems enough and you will cause coral death. Give them too much and you can cause hair algae problems which may smother your corals...
this is where reefers get in trouble. different corals have adapted to different trophic levels. we need to know the origin of the coral to know what trophic level the coral will do best in. we tend to generalize (sometimes poorly) corals as softies, LPS, PS, and non PS. for the mostish part they are grouped by the trophic levels at which they do best. do not confuse inorganic and organic nutrients when dealing with corals. in general softies do fine with inorganic nutrients, SPS do not. SPS however do need a lot of organically bound phosphates in order to feed to the zoax within them, which in turn gives the coral back those great amino acids/sugars you are so readily spitting back at me.
the original source of these nutrients needs to come from the capture of food by the SPS. hermatypic organisms the presence of inorganic
and can lead to the death of the coral. sorry, i can not find the article about phosphates and SPS growth from ReefKeeper about this. i will post it later when i find it, or if anybody else has the link handy that would be great. anyway. the phosphates interrupt the way these corals perform photosynthesis. it gums up the works. the calcium carbonate structure is just a byproduct of photosynthesis in a low nutrient environment. in other words the skeleton is a turd.
i have a lot of links and i can not find my link to a good easy description on how this works, but the graphic above should help you look for more information if desired.
of course for those that want softies this is not a problem. the higher inorganic phosphate levels do not get in the way of photosynthesis for the coral and can beneficial.
here is a reference for the inorganic phosphate levels in ocean surface water. 0.005ppm. in most of the studies i have found the upper limit for an oligotrophic system is 0.1 micro molar, which works out be about 0.009ppm. which works well with the value that is listed in the above link. which unfortunately brings up the problem that our tests are not nearly accurate enough to give us a decent picture of where are systems are trophic wise. we may think 0.03 is good, but when compared to 0.009, or even 0.005 it is not really very close.
I'm not trying to be mean, I'm just trying to understand your concepts better, or understand that you are regurgitating information that some other hobbyist has passed on to you without doing your own research... Just curious if anything.
was not taking any of this as being mean. i really enjoy a good conversation. i am also one that does not like people that regurgitate information without backing any of it up. if you feel that you need more info please let me know and i will hunt down more of the links that pertain your question. i have amassed quite a lot of links over the years.
i have been in this hobby for quite a long time. i have been reading and studying up on the phosphate cycle for almost as long once i learned a little more about what it actually is and how it pertains to our systems. there are a lot of deeeeeep rabbit holes of information that deal with phosphates and how our systems work with and against the supply of phosphates. we need to understand them in order to actually progress in this hobby. i do not have all of the information, but i think i have a good start on it.
