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SeaChem Fluorish Excel and Otocinclus - bad combination?

Joined
7 Jan 2021
Messages
146
Location
Nottingham, England
Hi all

I'm having quite a lot of trouble keeping my Otocinclus alive. I've had 18 so far since November, and 7 have died - 3 different Otocinclus species from 4 different sellers. They are fed blanched vegetables regularly and the tank is well planted, so are very plump, well fed and generally very active. There's rarely ever any signs of illness, it's so odd - they just suddenly drop dead.

The only possibilities I can think of is that (a) about 3/4 of them have come through the post on Ebay which may stress them further, and (b) something I'm adding to the tank is stressing them physiologically. The only two things I add to the tank are TNC Complete, dosed regularly to keep nitrates at 20ppm; and Seachem Fluorish Excel, 5mL added/day. There's not really any information on whether either of these are toxic to otocinclus. Fluorish Excel would be my prime suspect I think, given glutaraldehyde is a sterilant and supposedly Fluorish Excel's active ingredient is a derivative of glutaraldehyde.

If it helps at all my parametres are below (measured via API drop kit):

NH3: 0
NO2: 0
NO3: 10~20ppm
pH: 7.5
KH: 7
GH: 10

Tank size: 180L
Temperature: 25.5*C

Thanks everybody
 
Oto are fragile fish and die easily, and don't blame on Excel dosing. If dosed at recommended dosage (2 ppm initial and 0.4 ppm daily according to Seachem), Excel (glutaldehyde) has low toxicity to fish and shrimp. I have compiled toxicity test results from various sources below and feel safe to dose Glut based on the results.:

Toxicity of glutaraldehyde

96h acute Bluegill sunfishLC50 = 11.2 mg/L
Bluegill sunfishNOEC = 10 mg/L
48h acute Oyster larvaeLC50 = 2.1 mg/L
96h acute Green crabsLC50 = 465 mg/L
96h acute Grass shrimpLC50 = 41 mg/L
48h acute Daphnia magnaLC50 = 0.35 mg/L
Daphnia magnaNOEC = 0.32 mg/L
96h algal growth inhibition Selenastrum capricornutum ILm = 3.9 mg/L
Algal inhibition Selenastrum subcapitataIC50=1 to 1.8 mg/L
96h algal growth inhibition Scenedesmus subspicatusEC50 = 0.9 mg/L
Bacterial inhibition Sewage microbesIC50 = 25-34 mg/L
96h O. mykiss (Trout hatch rate)IC50 = 1.82 mg/L
96h C. dubia (Daphnia reproduction)IC50 = 4.7 mg/L

*EC=Effective concentration; IC=Inhibition concentration; LC=Lethal concentration;
NOEC=No observed effect concentration

I regularly dose 2 to 3 ppm Glut to my fish and shrimp tanks after WC, and I have never encountered death. Long term daily dosing may affect shrimp reproduction, but I have not tried it to find out.
 
Oto are fragile fish and die easily, and don't blame on Excel dosing. If dosed at recommended dosage (2 ppm initial and 0.4 ppm daily according to Seachem), Excel (glutaldehyde) has low toxicity to fish and shrimp. I have compiled toxicity test results from various sources below and feel safe to dose Glut based on the results.:

Toxicity of glutaraldehyde

....

I regularly dose 2 to 3 ppm Glut to my fish and shrimp tanks after WC, and I have never encountered death. Long term daily dosing may affect shrimp reproduction, but I have not tried it to find out.

This is reassuring, thank you for posting this :)
 
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