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- Jan 22, 2026
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Hey everyone,
I’m looking for help figuring out what’s gone wrong with my system after a forced downsize.
For a bit of background: I had a 55-gallon display with a 33-gallon sump running for well over a year. I was running rotating macro algae (chaeto and dragon’s breath) in the refugium and pulling out about a softball-sized clump every week. Everything was thriving.
My landlord saw the setup, wasn’t okay with the size, and made me downsize. I picked up a used Red Sea Reefer Gen 1 (roughly 28 gallons total) that turned out to be leaky, so I resealed and replumbed it and added a section in the sump to rotate chaeto. I moved everything into the Reefer about 6 months ago, and since then things have gone steadily downhill. I used the same live rock and sand (though, not all of it), it was all out of the water for less than 20 minutes.
Shortly after the downgrade, I had a breakout of red planaria. I treated the tank multiple times with Salifert Flatworm Exit, using a filter sock to catch the dying flatworms each time. After about four treatments, they have not come back. That was about 6 months ago.
Since the move, chaeto will not grow. I’ve bought new chaeto and re-added it multiple times and it just slowly melts away. Dragon’s breath fared slightly better, but eventually also died. I’ve lost hammer coral, 10+ heads of pulsing Xenia, a Goniopora, and at least 15+ trochus snails, and most of my remaining corals are either dying or very retracted. Yesterday I found my banggai cardinal dead. The API saltwater ammonia test is still reading high and looks to be around 0.5 ppm, while nitrite and nitrate are both testing at 0. For a while I was doing roughly 25% water changes every few weeks, but they didn’t seem to change the test readings or stop corals and inverts from declining or prevent the chaeto from melting, and in the last few months I’ve honestly started to lose faith and have been slacking on water changes.
Right now the tank has two clownfish; zoas that aren’t fully retracted but definitely don’t look happy; a Sinularia that is melting and will probably be dead soon; a toadstool that is totally retracted; Duncans that have been retracted for about a month; a candy cane coral that seems to be relatively normal; GSP that is fully retracted; and Discosoma mushrooms that are still alive but totally retracted. There are also hopefully two Pithos crabs hiding in the rockwork and some Scutus snails. I feed the clownfish very modestly, either frozen mysis shrimp or Hikari Marine S in small amounts. There's some aiptasia in the tank, but I'm hesitant to add berghia or any other livestock while things are still on a downward trend.
The system is a Red Sea Reefer Gen 1 (about 28 gallons total) with sump, a protein skimmer, a refugium section for chaeto (which is not currently growing), and an auto top off with a large reservoir. I use a dual-membrane RO unit for source water, and the product water measures 0 TDS. About 2.5 months ago I added these ceramic blocks and fit all 72 pieces into the sump and behind the rockwork:
Amazon product ASIN B0BYTVVDNNI soaked most of the new biomedia in Seachem Stability solution before adding it.
Water parameters (most recent):
I’ve attached photos of the tank and sump to give a better sense of the setup and livestock condition.
At this point I feel like I’m missing something obvious, and I’m worried about losing my remaining fish and corals, especially the clowns. Based on the information above and the photos, what would you check or test next, and what details would be most helpful for you all to see?
Thank you in advance for taking the time to look this over and help me troubleshoot.

I’m looking for help figuring out what’s gone wrong with my system after a forced downsize.
For a bit of background: I had a 55-gallon display with a 33-gallon sump running for well over a year. I was running rotating macro algae (chaeto and dragon’s breath) in the refugium and pulling out about a softball-sized clump every week. Everything was thriving.
My landlord saw the setup, wasn’t okay with the size, and made me downsize. I picked up a used Red Sea Reefer Gen 1 (roughly 28 gallons total) that turned out to be leaky, so I resealed and replumbed it and added a section in the sump to rotate chaeto. I moved everything into the Reefer about 6 months ago, and since then things have gone steadily downhill. I used the same live rock and sand (though, not all of it), it was all out of the water for less than 20 minutes.
Shortly after the downgrade, I had a breakout of red planaria. I treated the tank multiple times with Salifert Flatworm Exit, using a filter sock to catch the dying flatworms each time. After about four treatments, they have not come back. That was about 6 months ago.
Since the move, chaeto will not grow. I’ve bought new chaeto and re-added it multiple times and it just slowly melts away. Dragon’s breath fared slightly better, but eventually also died. I’ve lost hammer coral, 10+ heads of pulsing Xenia, a Goniopora, and at least 15+ trochus snails, and most of my remaining corals are either dying or very retracted. Yesterday I found my banggai cardinal dead. The API saltwater ammonia test is still reading high and looks to be around 0.5 ppm, while nitrite and nitrate are both testing at 0. For a while I was doing roughly 25% water changes every few weeks, but they didn’t seem to change the test readings or stop corals and inverts from declining or prevent the chaeto from melting, and in the last few months I’ve honestly started to lose faith and have been slacking on water changes.
Right now the tank has two clownfish; zoas that aren’t fully retracted but definitely don’t look happy; a Sinularia that is melting and will probably be dead soon; a toadstool that is totally retracted; Duncans that have been retracted for about a month; a candy cane coral that seems to be relatively normal; GSP that is fully retracted; and Discosoma mushrooms that are still alive but totally retracted. There are also hopefully two Pithos crabs hiding in the rockwork and some Scutus snails. I feed the clownfish very modestly, either frozen mysis shrimp or Hikari Marine S in small amounts. There's some aiptasia in the tank, but I'm hesitant to add berghia or any other livestock while things are still on a downward trend.
The system is a Red Sea Reefer Gen 1 (about 28 gallons total) with sump, a protein skimmer, a refugium section for chaeto (which is not currently growing), and an auto top off with a large reservoir. I use a dual-membrane RO unit for source water, and the product water measures 0 TDS. About 2.5 months ago I added these ceramic blocks and fit all 72 pieces into the sump and behind the rockwork:
Amazon product ASIN B0BYTVVDNNI soaked most of the new biomedia in Seachem Stability solution before adding it.
Water parameters (most recent):
- Salinity: 35 ppt
- Temperature: 76°F
- pH: ~8.1
- Ammonia: ~0.5 ppm (API marine)
- Nitrite: 0 (API marine)
- Nitrate: 0 (API marine)
- RO product water: 0 TDS
- I don’t have current readings for alk, calcium, or magnesium.
I’ve attached photos of the tank and sump to give a better sense of the setup and livestock condition.
At this point I feel like I’m missing something obvious, and I’m worried about losing my remaining fish and corals, especially the clowns. Based on the information above and the photos, what would you check or test next, and what details would be most helpful for you all to see?
Thank you in advance for taking the time to look this over and help me troubleshoot.

