Rainbow Shark flashing AGAIN! Ideas? Help?


Hi all,

Background -
I first joined this forum on June 6th, 2021. We thought we had it figured out last time because ammonia and nitrite levels spiked, most likely caused by a decomposing 6" rainbow shark that hide under the "under gravel filter" we installed and didn't realize for a few days. My two (now one) shark and yoyo loach are the first fish I got about a year ago. I absolutely cried hysterically over that first death and had to leave the house lol. I knew that first one would be bad. (I also hadn't received the master liquid test kit yet, and the levels taken the night before were all "fine"). I did a partial water change and worked hard to get levels back down. I have been doing liquid sampling of my 3 tanks (main - Shark in there, QT - a loach, 3 guppies, and a platy, and a Baby/Birthing tank) nightly so I can see how often and how large of water changes they really need (saw on YouTube, lmk if you think that's good or just stick with 25%/week PWC).

Emergency form -
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What is the water volume of the tank? 55 gallons
How long has the tank been running? About a year
Does it have a filter? Yes, Aqueon QuietFlow 75 HOB
Does it have a heater? Yes, Eheim 300w
What is the water temperature? Currently 82, it did go up to 84 a couple days ago when symptoms started, but don't think that would be issue?
What is the entire stocking of this tank? (Please list all fish and inverts.) 1 Pleco (7"), 1 Rainbow Shark (6"), Dojo loach (6-6.5"), yoyo loach (5"), 2 Dwarf Gouramis, 3 fancy guppies (+1 almost mature), 2 balloon mollies, approximately 30-40 molly babies (maybe 0.25" AT LONGEST currently), 3 forktail rainbowfish, 2 mickey mouse platys, 2 mystery snails, 1 assassin snail (not sure if he's still alive honestly)

How often do you change the water? About once/week
How much of the water do you change? About 25-30%
What do you use to treat your water? TankFirst Water Conditioner
Do you vacuum the substrate or just the water? Vacuum, alternating sides

*Parameters - Very Important
Did you cycle your tank before adding fish? Yes
What do you use to test the water? API Liquid Master Test Kits
What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.
Ammonia: 0 ppm
Nitrite: 0 ppm
Nitrate: I believe 40 ppm, may be more like 60
pH: 7.4

How often do you feed your fish?
3-5x per day (I have been very ill and do forget when they have eaten sometimes)
How much do you feed your fish?
About what the instructions say (as much as they can eat within 3 minutes). We have a wide range of food to try to offer diversity to their diet and serve surface and bottom dwelling fish. A "normal feeding" is a pinch of flakes, a pinch of tropical granules (probably around 20), 4 shrimp pellets, and usually just one algae wafer a day for the pleco. Brine shrimp are given once every couple days (was their evening meal yesterday). When those are fed, that is the only food given for that feeding time. Yesterday, I did feed a couple of defrosted peeled peas.
What brand of food do you feed your fish? Flakes are Omega One "Super Color Flakes," tropical granules are Aqueon, shrimp pellets are aqueon, and algae wafers are API, Omega One Frozen brine shrimp
Do you feed frozen or freeze-dried foods? Frozen Brine Shrimp

Illness & Symptoms
How long have you had this fish? Almost a year :(
How long ago did you first notice these symptoms? 2 days ago
In a few words, can you explain the symptoms? Flashing, loss of appetite
Have you started any treatment for the illness? Not yet
Was your fish physically ill or injured upon purchase? No
How has its behavior and appearance changed, if at all? Only see flashing and loss of appetite with rainbow shark, the dojo loach is quite inactive unless he's eating everything in sight (I think he's always acted that way), don't see any appearance change in any of them.

Explain your emergency situation in detail.
First had issues on June 6th, where I found out the ammonia, nitrite, and nitrates had all spiked as result of decomposing fish. Levels have gotten back on track. The last couple of days, I have noticed the shark flashing. Yesterday was just a few times, this morning alone I've seen it several. Could this just be due to high nitrates? I looked up nitrate poisoning, and I don't think they have those symptoms. We bought new fish, BUT they are in a quarantine tank. The only changes that have been made recently, were the larger baby mollies were transferred from baby tank to main tank. When symptoms first began, the temperature went up to 84 (I don't think abruptly), but it has been a steady 81-82 for the past couple days.

Thanks for your advice ahead of time!


Im really not to sure. It doesn't seem too severe at the moment. I would think that it's just from the super high nitrates. Do 50% wc's every few days to get that on track, and add some houseplant roots (like pothos) to suck up nitrates. Check out my article below on the houseplant topic.
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Id cut back on the feeding too - that wont be helping the water quality.
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I did a 50% water change and he stopped flashing the next day. I’m also resisting the over feeding lol. Thank you!
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