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Unread 12/09/2017, 10:37 PM   #1
BobJones02
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Bioload too low?

I have a 125 gallon reef with a 55 gallon sump and about 150 lbs of live rock. I've had only 2 clowns and a chromis in there for the last 4 months, and I've been noticing my corals declining/receding. parameters are where they should be (8.4 dkH, 420 cal, 1240 mag(a little low)), so could it be that I don't have enough fish?


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Unread 12/09/2017, 11:44 PM   #2
Lsufan
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Do u test no3 & po4 ? Although I don’t know about your system specifically, it definitely can be a issue. U would need to say more about your system to be able to get helpful answers. Things like the type of corals, your po4 & no3 results & whatever else u can think of about your system.

I find with really low nutrients that the coral just don’t thrive, not necessarily die. They don’t show great polp extension & grow extremely slow like they are starving. Over time it can end up killing them if they aren’t getting any food. The types of corals also make a difference.

My first couple years of getting into corals they all grew really slow & didn’t show much pe. They survived but that was about it. I always kept low nutrients because all the research I did said to keep 0 no3 & po4. I did a experiment of dosing no3 & sure enough they started looking better. I didn’t want to rely on dosing no3 so I added more fish & started doing biweekly water changes instead of weekly. Once I stopped reading 0 no3 & po4 on my tests is when my corals started to thrive. I now keep between 1 & 2 ppm no3 & a little po4 & it seems to be working well


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Unread 12/10/2017, 12:47 AM   #3
BobJones02
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I thought testing for nitrate and po4 would be useless since algae is always consuming it?


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Unread 12/10/2017, 01:05 AM   #4
Jon0807
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Some people keep coral only systems without any fish at all. So I don't think that's the problem. But then they do feed their corals. If you're planning on only keeping those fish, you might want to look into some coral food and start spot feeding.


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Unread 12/10/2017, 06:04 AM   #5
der_wille_zur_macht
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Quote:
Originally Posted by BobJones02 View Post
I thought testing for nitrate and po4 would be useless since algae is always consuming it?
That's not specifically true. There can be cases where algae is consuming it quickly, but in those cases there's usually an issue where nutrients are locked up in a form the test kit can't read anyways. Unless you have out of control algae growth and a suspected source of bound nutrients in your system (ie really dirty live rock), your statement is usually not true.

Reef environments are very complicated. Our test kits are only able to measure certain chemicals in certain forms, when they're dissolved in the water column. What we really want to know is the total nitrogen and phosphorus available in the tank, but the best we can do is measure nitrate and phosphate. In most cases, these are good stand-ins, and measuring them is very helpful. The tests work in cases where the nutrients are primarily arriving via food, etc - and going through regular breakdown cycles. The tests are not effective when the nutrients are bound organically in the system or in some undissolved solid.

But honestly I don't think any of that is relevant in your case.

It certainly could be the case that your corals are nutrient starved. It's fairly easy to find out. Start feeding a lot more, keep an eye on nutrients and be careful about kicking off an algae plague. If the corals improve, you're all set.

It's fair to point out though that there could be a number of other causes. Flow and lighting come to mind. We'd need to know more about your system to diagnose.


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Unread 12/10/2017, 08:14 AM   #6
JTL
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I recently read an old and long thread about this because my corals are not doing as well as I would like. I have <.25 NO3 and zero PO4. I have no algae and cannot grow chaeto. I am going to feed more and stretch out my water changes and see if that helps.

I am also going to throttle back my lights a bit. I read that 250 PAR or thereabouts is a sweet spot for sps. The obvious is that nutrients, lights, flow and the big 3 all work in concert so I just need to lightly tweak things until I get the desired results.


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Unread 12/10/2017, 01:05 PM   #7
BobJones02
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Well, looks like I'm going to add a few fish, but until the quarantine process finishes, I'll just throw in a bunch of extra food. Whenever I do feed my frogspawn, it gets really extended the next day, so maybe increasing nutrients will help.


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Unread 12/10/2017, 05:52 PM   #8
der_wille_zur_macht
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This is treading off the beaten path of scientific proof, but I've seen countless examples where no matter the nutrient or food present, corals seem to do better with an "appropriate" fish load. Yes, there are frag growout systems with zero fish that are successful, but in terms of mainstream tanks, it seems like having lots of fat and healthy fish is a good indication that the corals will do well. Maybe it's the form of the nutrients or food - perhaps corals prefer fish poop to raw food in some cases.


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Unread 12/11/2017, 10:15 PM   #9
Timfish
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It doesn't seem to be common knowledge that corals are primary producers in reef ecosystems. As such they are pulling nitrogen (organic urea and amino acids and inorganic ammonia and nitrate) and phosphorus (organic and inorganic PO4) from the water. And by doing so they are directly competing with algae.

One of the curious discoveries research has recently found is corals are nitrogen snobs. This paper looked at the effect nitrogen and phospahte dosing had on corals and found "the response of corals to increasing nutrient availability was context-dependent, . . . For example, naturally occurring enrichment from fish excretion increased coral growth while human-mediated enrichment tended to decrease coral growth." (Read "human-mediated enrichment" as agricultural runoff and sewage.)

Phosphate is essential for corals to utilize nitrogen and if they don't get enough it really messes them up. This paper looked at phosphate restriction on corals maintained for several years in aqauria under tightly controlled conditions. The researchers found "the undersupply of phosphate severely disturbed the symbiosis, indicated by the loss of coral biomass, malfunctioning of algal photosynthesis and bleaching of the corals. In contrast, the corals tolerated an undersupply with nitrogen at high phosphate concentrations without negative effects on symbiont photosynthesis,"


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