Phosphates are the key to unlocking coraline?

Retro Heat · Sep 4, 2023

My 15 gallon iM tank is about 1 year old now. After the ugly stage... my coraline algae growth took off. Fast forward about 6 months and I started to notice that my explosive algae growth started to taper off. It got to the point that there was no more new growth and the old coraline was being eaten away by my cleanup crew. Other than that... My tank was looking great. But, a certain zoa frag that I grew from 1 polyp to about 40 polyps started to melt.

Here a little background. I'm pretty obsessive when it comes to my tank. I test alk everyday (Hanna). I test calcium, mag, nitrates, ammonia, ph, salinity every week right before my 15% water change. The only thing I was never good at testing was phosphates since I have an aquaforest test kit and I'm not able to distinguish the slight difference in the shade of blue. I manually dose every day red Sea alk and calcium. And, I dose mag and trace colors every week after my water change. I even change out my filter pads 2x a week. Let's just say that I have fun taking care of my tank

Well, I noticed that my coraline algae growth basically stopped and my zoa colony melting was my tipping point. Since all my other specs were good (9dkh, 425cal, 1400mag, 1.025 salinity, 5ish nitrates, 8.0-8.1ish ph) I pretty much deduced that phosphates were probably my problem. So, I bit the bullet and bought the ULR phosphorus tester + the HR nitrates tester. Hanna tested my nitrates to 12ish and my phosphates to 0.6.

Well, I threw in a big bag of phosguard and I kid you not... The very next day... I started to see purple dusting on my frag rack and about 5 of my melted zoa polyps were starting to open again. Keep in mind that my frag rack has been in my tank for about a month and has never shown any signs of coraline growth. I kept the big bag of phosguard in for 4 days and I can already see spots of coraline growing on my wavemaker and the back glass as well. I tested my phosphates after 4 days and it now reads at 0.25. Not great but a lot better. I just replaced the phosguard (with a smaller amount this time) and I'll keep running it till I can get it under 0.1.

I just found it interesting that given that everything else has remained equal... All it took was for me to lower my phosphates to get my coraline to start taking off again. This might be helpful to anyone else out there having trouble growing coraline.

CoralB · Sep 7, 2023

Too high or too low ( like zero) of phosphate can be a problem . My tank is happiest with my phosphates between 0.1 and 0.2 . Once you get to your spot just remember consistency and patience are key in this hobby

Thanks for sharing your observation

Retro Heat · Sep 8, 2023

I'm starting to think somewhere between 0.1 and 0.2 would probably be best for me as well. I've been able to get it down to about 0.23 right now and everything looks really good right now. My LPS (acans, cyphastrea, frogspawn) all look super puffy right now. Also, my frogspawn is starting to throw lots of new baby buds off his skeleton. The cyphastrea is starting to encrust on the spot I placed him and I see some new polyps as well. Even my monti is starting to encrust as well. But, my leather, zoas and mushrooms look good too. I think if I go too low, my softies might start to suffer since they like things a little dirty (just not too dirty).

Floyd- · Sep 8, 2023

I also keep my phosphates at about .1-.2 without issues. More than .2 I would be worried and less than .1 I get worried about bottoming out.

water logged · Apr 19, 2024

Retro Heat said:
My 15 gallon iM tank is about 1 year old now. After the ugly stage... my coraline algae growth took off. Fast forward about 6 months and I started to notice that my explosive algae growth started to taper off. It got to the point that there was no more new growth and the old coraline was being eaten away by my cleanup crew. Other than that... My tank was looking great. But, a certain zoa frag that I grew from 1 polyp to about 40 polyps started to melt.

Here a little background. I'm pretty obsessive when it comes to my tank. I test alk everyday (Hanna). I test calcium, mag, nitrates, ammonia, ph, salinity every week right before my 15% water change. The only thing I was never good at testing was phosphates since I have an aquaforest test kit and I'm not able to distinguish the slight difference in the shade of blue. I manually dose every day red Sea alk and calcium. And, I dose mag and trace colors every week after my water change. I even change out my filter pads 2x a week. Let's just say that I have fun taking care of my tank

Well, I noticed that my coraline algae growth basically stopped and my zoa colony melting was my tipping point. Since all my other specs were good (9dkh, 425cal, 1400mag, 1.025 salinity, 5ish nitrates, 8.0-8.1ish ph) I pretty much deduced that phosphates were probably my problem. So, I bit the bullet and bought the ULR phosphorus tester + the HR nitrates tester. Hanna tested my nitrates to 12ish and my phosphates to 0.6.

Well, I threw in a big bag of phosguard and I kid you not... The very next day... I started to see purple dusting on my frag rack and about 5 of my melted zoa polyps were starting to open again. Keep in mind that my frag rack has been in my tank for about a month and has never shown any signs of coraline growth. I kept the big bag of phosguard in for 4 days and I can already see spots of coraline growing on my wavemaker and the back glass as well. I tested my phosphates after 4 days and it now reads at 0.25. Not great but a lot better. I just replaced the phosguard (with a smaller amount this time) and I'll keep running it till I can get it under 0.1.

I just found it interesting that given that everything else has remained equal... All it took was for me to lower my phosphates to get my coraline to start taking off again. This might be helpful to anyone else out there having trouble growing coraline.

Thanks I have been trying to grow coraline for a few months, with no luck, but I just tested my phosphates at 0.5 and 1 day after adding phosguard my corals are looking better. I was using the Aqua one test kits & they are useless. They are so inaccurate & the chart was not correct.