Advice for a Struggling Refugium?

gfinan · Jun 12, 2026

Hey y'all,

I've had my tank running since early February this year. I have a 75 gallon tank with a 25 gallon sump. I have a protein skimmer running (Bubble Magus Curve 5) and a refugium that has been stalling out, it seems. It's somewhat demoralizing, because everyone says that refugiums are so easy

... Anyways, I have a couple of questions I'm hoping someone can answer:

1. Do you need to have enough flow to continuously flip your chaeto?
-If you do, can anyone provide some suggestions? I tried to put a Jebao SLW-5 in there and it got horrendously clogged with chaeto. I ended up just manually flipping the chaeto ball every day or two.
2. Is my light just really bad? I have the ChaetoMax 2-in-1 LED... haven't heard great things about it, but some people use really crappy lighting and still get OK chaeto growth.
3. Do I not have enough chaeto to handle the bioload? I started with (and basically maintained) ~3 ounces of chaeto. My nitrates have been between 5-10 ppm (closer to 10 generally) since the refugium has been running, but phosphates have been quite high (0.2ppm) and I've struggled to keep phosphates under control.
4. Magnesium was really high for a month or two. Greater than 1550 ppm. Does that hurt chaeto growth? Magnesium has since come down to ~1350 ppm, but I haven't seen any changes or improvement.

Some other details:
I was using the Brightwell ChaetoGro for a week or so, but this actually increased magnesium while I was struggling with #4. So, I stopped adding that into the sump.

Due to my concerns from #3, I bought another 2 ounces of chaeto, but it died very soon after going in the sump. I think it got too hot in shipping, but when it died it seemed to take out my previously healthy chaeto with it. Now i only have a small amount left (maybe 2 ounces).

My tank is currently in a fallow period to treat marine ich, with the temperature at 81 degF. Still, with zero fish in the tank, my nutrients were out of control from the small amount of feeding I was doing to help keep my CUC and corals alive. I just feel like the refugium is doing nothing. In the 3 months it's been running, I have never had to trim it down because the growth was so small.

The sump chamber where I have the refugium is quite stagnant. I increased the overall flow in my system to try and shake things up in there, but it doesn't seem to help. I'm considering adding an air stone for some flow.

Any insight you all can provide, whether it relates to those questions above or not, would be greatly appreciated!

Thanks in advance,
Gabby

Boehmtown · Jun 12, 2026

Just leave it. Your skimmers doing the filtration. Just leave it. Stop dosing chaeto grow until it's really going later. Think of it like a battery. It'll expand and die off depending on the excess nutrients. If you grew more, your nitrates would tank. Use chemi pure elite or rowa phos at half strength, maybe quarter, .2 isn't that bad, take your time lowering it. You can try switching what you're feeding to help reduce Phosphates, or rinse the food, some foods are very high in pnospiantes. Always keep an eye on it. Trim off non healthy stuff , keep it clean. It's not the light, it's not the flow, it's working as it should. If your organics and nutrients rise it'll pick up pace. It technically completes with your corals but provides a ph boost when run over night and other benefits. So you want it there, and growing, but as slow as possible. It's like a nutrient shock absorber.

Saltsavage504 · Tuesday at 2:03 PM

gfinan said:
Hey y'all,

I've had my tank running since early February this year. I have a 75 gallon tank with a 25 gallon sump. I have a protein skimmer running (Bubble Magus Curve 5) and a refugium that has been stalling out, it seems. It's somewhat demoralizing, because everyone says that refugiums are so easy ... Anyways, I have a couple of questions I'm hoping someone can answer:

1. Do you need to have enough flow to continuously flip your chaeto?
-If you do, can anyone provide some suggestions? I tried to put a Jebao SLW-5 in there and it got horrendously clogged with chaeto. I ended up just manually flipping the chaeto ball every day or two.
2. Is my light just really bad? I have the ChaetoMax 2-in-1 LED... haven't heard great things about it, but some people use really crappy lighting and still get OK chaeto growth.
3. Do I not have enough chaeto to handle the bioload? I started with (and basically maintained) ~3 ounces of chaeto. My nitrates have been between 5-10 ppm (closer to 10 generally) since the refugium has been running, but phosphates have been quite high (0.2ppm) and I've struggled to keep phosphates under control.
4. Magnesium was really high for a month or two. Greater than 1550 ppm. Does that hurt chaeto growth? Magnesium has since come down to ~1350 ppm, but I haven't seen any changes or improvement.

Some other details:
I was using the Brightwell ChaetoGro for a week or so, but this actually increased magnesium while I was struggling with #4. So, I stopped adding that into the sump.

Due to my concerns from #3, I bought another 2 ounces of chaeto, but it died very soon after going in the sump. I think it got too hot in shipping, but when it died it seemed to take out my previously healthy chaeto with it. Now i only have a small amount left (maybe 2 ounces).

My tank is currently in a fallow period to treat marine ich, with the temperature at 81 degF. Still, with zero fish in the tank, my nutrients were out of control from the small amount of feeding I was doing to help keep my CUC and corals alive. I just feel like the refugium is doing nothing. In the 3 months it's been running, I have never had to trim it down because the growth was so small.

The sump chamber where I have the refugium is quite stagnant. I increased the overall flow in my system to try and shake things up in there, but it doesn't seem to help. I'm considering adding an air stone for some flow.

Any insight you all can provide, whether it relates to those questions above or not, would be greatly appreciated!

Thanks in advance,
Gabby

Look up best pump for cheato tumbling and u will see r2r forum about it. A guy came up with a great way to tumble it and his looks very healthy and happy lol

gfinan · Tuesday at 2:15 PM

Saltsavage504 said:
Look up best pump for cheato tumbling and u will see r2r forum about it. A guy came up with a great way to tumble it and his looks very healthy and happy lol

thanks! I have an air stone in there now and thats been helping it a bit, but im sure having a pump to keep it spinning would be better