Phosphate levels: a never-ending struggle

coralline

coralline

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Hout Bay, Cape Town
HI folks,
I'm really struggling with PO4 levels which I just can't get down to acceptable levels. Here are the fundamentals to put you in the picture:
My system:
  • DT is six foot (1.8m).
  • +- 700ltr system.
  • 4 foot DSB in sump (playpit sand 15cm deep).
  • 30 cm wide skinny overflow on back of tank (in middle).
  • Reef OctX200 in-sump skimmer (works like a dream).
  • 3700 ltr return pump.
  • Auto top up system using RO water.
  • 2 x SunSun 12000ltr/hour circulation pumps (1 runs during the day only)
  • Lots (about 50-70 kgs) of DIY rock (made from portland cement, brushed coral etc, cured and rinsed for 2 months according to general guidance/practice).
  • Lighting: LED system (DIY - 10x10W white 7000K, 10x3W blue, 9x3W white 10,000K and 9x3W white 20,000K); now only running 10x3W whites until Arduino is programmed and installed).
The system has been running for about 9 months now, and the DSM looks fine but doesn't have as much life as I've seen in others, and there are areas where detritus gathers...
In the last 2 chambers of the sump, I also have a filter sock with ceramic filter media in from when I started the system, which I've been meaning to remove. I also have some BioBalls (only about 30 or so) which I have also been thinling of removing as well.
In the 2nd last section of the sump, I have made a small refugium with some caulerpa which is lit for about 12 hours during the evening. It is home for a thriving colony of pods :)
I was using a DIY phoshate reactor (from an RO unit) which was housing about 700 ml of 'ORCA' GFH phosphate remover. But, I think this is saturated now, so needs to be replaced/recharged.
Livestock:
  • 10 fish (all small)
  • 1 lobster
  • 2 shrimps
  • 1 hermit crab
  • 1 urchin
Corals - none yet (other than a few brown zoas which are actually thriving and spreading!) until my phosphates get down! Also, I only recently finished my DIY LED lighting system...
Water parameters:
  • PO4. Levels: 0,5ppm, validated at LFS; NO3: 0.5ppm; pH: 8.3; KH: 11.6
  • All Salifert Test Kits
I don't add Kalkwasser/Calcium/ Iodine/Strontium/Magnesium yet (until I get corals once my PO4 is lower).
I started the tank off in January very slowly with a couple of clown fish, and built it up gradually. I also used Brightwell Bacteria supplement.
Over the last 5 weeks I have been adding 13ml of Red Sea NO3:pO4 - X daily in the hope of reducing the phosphates, but to no avail!
I do 60ltr water changes every 2 weeks, and even tried smaller more frequent water changes, still no reduction in PO4. My RO water measures 0 TDS, and my fresh salt mix (Red Sea Coral Pro) measures 0ppm PO4...
I also removed about 15 Kg of the DIY rock, since I tried keeping a piece in freshly made salt water (which measured 0ppm PO4 to start wth, and it raised to 0.5ppm after a few days). My suspicion is that it is all the DIY rock that is somehow leaching PO4 into the water... But why?! I love the creative DIY rocks I made and would hate to have to remove it all and buy Live Rock to replace it!
So, you views will be most welcome. Sorry for the long story, but I'd rather give all the facts up front.
Many thanks in advance :thumbup:
 
Grow cheato in the sump should make things a lot better if dealing with phosphates or a algea Scrubber is also another alternate.
 
yip rhowaphos does the job and is a long term sollution
 
Orca Phospha-Guard, Said to work like a charm, a little new on the market so not much info but there are some threads.
And so is Rowa, if you thinking of media
 
Ayoob said:
I would still prefer the cheato in sump less expensive
Click to expand...

indeed,only prob is it takes a while to addapt and start growing but once it starts,it never stops ,and as it grows it sucks up your nutrients 123:thumbup:
 
You do not have a crazy nutrient problem.

Yes you could lower them a bit, but it's so easy if you just renew your PO4 remover.

I have seen fantastically healthy corals including SPS under 0,5 ppm pO4.

Don't panic, just use the recomended products to remove them.;)
 
coralline said:
I was using a DIY phoshate reactor (from an RO unit) which was housing about 700 ml of 'ORCA' GFH phosphate remover. But, I think this is saturated now, so needs to be replaced/recharged.
Click to expand...


Bob the (reef)builder said:
You do not have a crazy nutrient problem.

Yes you could lower them a bit, but it's so easy if you just renew your PO4 remover.
Click to expand...

Sorry was also speed reading - As Bob says try replacing your GFH media - maybe try another brand if you want to.

GFH has quite a high capacity to take up phosphate. For 700l I'd recommend about 250g of ROWAPHOS or similar, and then only replace when you see a) signs of excessive phosphates eg. hair algae, or B) when the phosphate levels rising. Should last for at least 6 months though, if not longer.
 
How did you seed your DSB? What is the flow rate across the DSB. sound too slow and that is the reason for the detritus. How wide is your sump from front to back? What is your return pump rating?

How porous is the DIY rock? Are there really enough space on and in the rock for beneficial bacteria?

I think part of your problem is that your return pump is too small. And you do not have enough turnover via your sump. So even with your refugium and cubes or phosphate remover. You are simply not passing enough water to be treated. Basically starving the refugium. Creating settlement on the DSB.
 
@corraline, @RiaanP is the go to man in term of DSB's, take note at what he says.
 
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RiaanP said:
How did you seed your DSB? What is the flow rate across the DSB. sound too slow and that is the reason for the detritus. How wide is your sump from front to back? What is your return pump rating?

How porous is the DIY rock? Are there really enough space on and in the rock for beneficial bacteria?

I think part of your problem is that your return pump is too small. And you do not have enough turnover via your sump. So even with your refugium and cubes or phosphate remover. You are simply not passing enough water to be treated. Basically starving the refugium. Creating settlement on the DSB.
Click to expand...

Hi Riaan,


Thank you for you post - your experience and expert advice is greatly appreciated;).

So a quick summary of my DSB to answer you questions:
I seeded the DSB with about 4 cups of sand from established DSBs (from 2 different DSBs actually)
The return pump is a Sicce Ultima, rated at 3700 lt/h. the head is about 1.5 meters.
The sumps is divided into 2 linked DSBs - the 1st sump tank has a 1st section for the inlet from the DT and the skimmer, this is 50cmx25cm; the 2nd section of the 1st sump is a DSB which is 50cmx35cm; the 2nd sump has a DSB which is 50cmx80cm; then there is a small refugium which is 50cmx14cm; and then the return pump chamber which is 50cmx14cm. Sand depth in the DSB is actually 13cm, and water depth is 14cm above the sand (and 27cm in the inlet section, refugium and return pump section).

The DIY rock is fairly porous - the cement/coral/salt mix was quite wet when I made the rocks, so I guess it's not VERY porous. Each rock is fairly heavy for it's size. But I do have a lot of rock in there, so I would say there is a lot of surface area for bacteria.


I was always worried about the pump size considering the volume of the tank, but several people (at the LFS and on MASA) told me that 3500lt/h will be enough. What you say about the flow through the sump and DSB makes good sense... Perhaps up the return pump to 4500lt/h? I recall you talking about the 'flake test' or something like that, where you let a flake of fish food sink in the DSB and it should not just sink down to the bottom but move through the DSB (or something similar to that:p). I don't have that much flow now, so clearly I need more!

So the big question... In your experience, do you think that increasing the return pump (and therefore flow through the DSB) will not only reduce the amount of detritus deposits but also increase the bacteria colonies and life in the DSB? And the impact of that on my phosphate levels? Obviously the nitrogen cycle doesn't address PO4, but are you thinking the accumulation of detritus is the cause of the PO4 levels?


I'm happy to change my sump configuration if you recommend that - I need to do something to reduce my PO4. Otherwise I'll just need to spend a small fortune on Rowaphos! Or change all the DIY rock for live rock... (I still don't see why the CIY rock is leaching phoshates). I still like the DSB concept and want to get it right.

If you're in the Northriding area and have 5 minutes to spare, I would infinitely grateful if you were willing to stop by and see it running (and make suggestions on how to improve;)).

Cheers bud:thumbup:
 
Great detail and questions here coraline. The flow over your sump should be more to reduce settlement and increase contact volume. A dsb can take a long time to mature. I have yet to hear of a hard and fast time frame, as there are so many factors involved here. Remember that the "life" that you see in the dsb, are only the workers that help to turn over water into the anaerobic regions of the dsb. The actual bacteria are already busy colonising in layers.

I hate to say it, but your live rock sounds too dense to be of benefit. If you suck it does it feel porous? High quality live rock is much better. Three pieces of bad rock together create a dead zone with no flow and allow detritus to build up there, whilst giving no filtration benefit. One piece of good rock allows good flow around it and houses aerobic and anaerobic bacteria on a huge surface area. So it's definitely a case of quality beating quantity hands down.

All of this still doesn't address your phosphate problem, which as you've pointed out will not be readily consumed in the dsb. Your first course of action will be to free flow your system. Remove any bioballs that are collecting detritus. Clean any mechanical filtration such as socks etc on a daily basis. Clean your skimmer neck every couple of days or so. Let your skimmer skim nice and wet, but remember to watch the salinity.

What type of food do you feed your fish and inverts? Are you observing that they consume all of it in a short time? You should aim at increasing water changes to about 15% per week.
 
Hi Corralline - please show us pictures of your tank and sump? As been said before - do you run any chemical filtration already? Do you use macro-algae in your sump, ie chaetomorpha?

What corals do you have in your tank?
 
Albert Terego said:
Quote: Originally Posted by Broder I hate to say it, but your live rock sounds too dense to be of benefit. If you suck it does it feel porous? Pics please I have to see this
Click to expand...

Remember,,, Klein hapies... :lol:
 
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