No3 and Po4 read 0 but algae grows

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Seeking some advice please.

Currently Nitrates and phosphates are reading 0 but I’m still having algae growth. Looks like green hair algae, bryopsis.

Will post some more recent photos later when the lights are on.

Tank is +- 300l
SG - 1025
Kh - 8.3
Ca - 480
Mg - 1440
Temp - 25.5-26

Skimmer - Curve 5
Light - 6x39w T5 unit (8hrs/day)
Flow - 1 x Jebao Ow-40, 1x sun-sun 6000lph pump

Return - 3000lph

Fish - 3 Chromis, 1 Copperband, 2 clowns, 1 Mandarin.

Coral - mostly Sps, some LPS, zoas.
The SPS are doing well, some of the LPS are looking a little pale.

Dosing 2 part daily, tank parameters are stable.

Feeding a mix of blended seafood (copperband loves) 2 x per day - would say about 1 block equivalent.
Will also feed 1 block Mysis one to two days a week.

My questions:

1. Could I be getting a false reading of No3/po4 because algae is eating up all the nutrients?

2. If I feed more to increase nutrients surely I’m just fuelling more algae?

3. If I feed less are my corals going to starve?
 
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RiaanP

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1. Could I be getting a false reading of No3/po4 because algae is eating up all the nutrients?
yes, most likely.

2. If I feed more to increase nutrients surely I’m just fuelling more algae?
any excess waste not taken care of would help algae growth

A cube frozen food per day for 7 fish is a lot. And the Chromis and clowns are not really big fish either with high feeding requirements. Chromis would actually do better with smaller feed but more frequently during the day. The Copperband and Mandarin would both compete for the same food source. Not really ideal in your tank size and that is why you have to feed frozens so much. Do not get any wrasses or fish that will also compete for copepods. Even a Sixline will out compete both the Copperband and Mandarin.

You do not mention what else makes up your filtration in your sump. Having to feed so much frozen food per day would force you to have more filtration capability than normal for this size tank. Can almost compare your tank to a NPS system with only corals that must be target fed a lot per day, with minimal fish load.
 
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Thanks, that makes sense.

Yes, I know the copperband and Mandarin will compete - but the copperband is eating frozens nicely.

I was running an oversized skimmer, but have since moved down to the curve 5 which is more appropriate.

I am running filter socks as I can.
I have started to remove the phosguard because I feel like nutrients are getting too low.
 
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I had the same issue shortly after swapping to my bigger tank. No3 and PO4 zero but had a green hair algae problem. (far worse than yours judging y the pics) Eventually, I decided it was down to the green hair algae using all available nutrients for growth so the tests measured 0, which is not a false reading, there was none in the water column because it was in the algae :)

Algae need nutrients to grow, it also needs light, the more light it has the more nutrients it use to grow. If you nutrients measure 0 then there is enough light to grow algae fast enough to pull all the no3 and po4 out the water.

I needed something to get ontop of the problem and since no3 and po0 were already I turned the lights down a little bit (not a huge change, just enough to get the upper hand). This made all the difference to me. In my case I dropped the light brightness from 50% to just under 40%. And once I got on top of it it became much easier to remove (hair algae gets soft and starts to melt away making it easy to siphon off).

Since then I have been able to turn them way back up again (currently at 80%), because I did it very slowly a balance was maintained, eg: my tangs will keep algae in check if it is just starting on a rock but won't eat hair algae once it is long. Most the rock surface are now caked in coraline which resists other algae growing over it and since there is no3, po4 in the water I can use carbon dosing to keep the amount at the level I want.

I see your list doesn't include an algae eater so you might want to look at adding one, though you probably need to first get the upper hand.

tldr:
1) yes, your nutrients are in the algae
2) yes, if the algae is there and fed it will grow more
3) No, once there is less algae, there will be more of the available for other things, including corals. Plus most the coral's energy is probably coming from your lights anyway, you'll want some nutrients available for them by there are not fish.
bonus) A fish that eats the algae and poops it back into the water will recycle those nutrients into the water
 
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That makes sense to me yeah.
Cool, going to bring my light time down a bit, and see if I can get ontop of it by removing the algae manually too.
 
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Bud from my experience if you have Bryopsis, you can run your NO and PO down to zero, move your light where ever you want to and that stuff won't flintch.

I took a rock with some on and put it in my QT tank in the garage with no light and a cover, after 3 months in there it had not grown but was still perfectly healthy.

It is a invasive pest brought into your tank on live rock and frag plugs. Short of stripping your tank down and starting from scratch with dry rock and dead sand, cutting every coral off its base, attaching it to dead rock and starting again you left with the flucanzole option.

Others may differ in opinion but a battled that Bryopsis for 8 months, ran my nutriants so low I killed most of my corals and it still grew wild.

Normal hair algae is relatively easily controlled with nutrient management. So a proper ID of your problem algae is important.
 
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Definitely agree there - doing monthly 10% water changes. Not running carbon, took my phosguard out as I thought it would drive phosphates too low

I think my problem initially came from overfeeding, so I’m hoping to get it under control by cutting down on the feeding and regaining the balance.

Running filter socks as I can (only recently put one back in).

Bryopsis for sure, but hair algae too. Luckily not too much on the rock but mostly sandbed.
 
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I would run fluconazole to get rid of the bryopsis. No other way to get rid of them and they spread quickly.
NO3 and PO4 are not the only elements that can fuel GHA growth. Dissolved organics in the water that is not removed by the skimmer can cause nuisance algae outbreaks even if your NO3 and PO4 are under control. Imo I would run activated carbon to clean the water. 10% monthly not enough to clear out the organics build up.
 
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Looks like bryopsis - but also looks like it’s melting.

I’ve removed my sandbed over a month, and siphoned algae but it keeps growing.

Don’t want a refugium in the display!
 
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Have been told my excess of blue light and phosphates (although reading zero) may be causing algae. T5’s are the following: 4 x blue plus and 2 x coral plus - all 6 months old.

My approach now is to feed Red Sea coral nutrition A+B to try and give the corals what they need, while manually removing algae.

Is it worth trying to use a phosphate remover, or is it risky to coral health?
 
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Filter sock, curve 5 skimmer, monthly water changes. Currently barebottom so suck detritus out from dead spots
 
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OK try and get some media that removes No3 and Po4 or IMO I'll cut back on feeding split the waterchanges to everyweek one cut down on a hour or two lights
 
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Did you test Parameters all of them as lps I know love extra nutrient in water and won't go pale about it it wil rather look better yes so it might me something bigger
 
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I would run fluconazole to get rid of the bryopsis. No other way to get rid of them and they spread quickly.
NO3 and PO4 are not the only elements that can fuel GHA growth. Dissolved organics in the water that is not removed by the skimmer can cause nuisance algae outbreaks even if your NO3 and PO4 are under control. Imo I would run activated carbon to clean the water. 10% monthly not enough to clear out the organics build up.

Agree, and just rent a seahare, problem solved
 
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Even though readings of phosphate show 0, I know the phosphate is present due to the algae growth.

I am now using some phosguard to try and pull the phosphates out quickly and outcompete the algae. Through this phase I will be feeding part a and b coral nutrition to provide nutrients for corals.

Have also reduced my photo period from 9hrs to 7hrs.

Hopefully algae starves out the algae
 

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