How would you treat this ill clown loach ?

It looks like it could be ich. Do any other fish have those tiny white specks? I would do a large water change with vacuuming. I'm old school & prefer dyes like malachite green to treat ich, some have good luck with table salt.

Pick a treatment & stick with it for at least 14 days. It helps to raise the temp to low 80s to speed up the ich lifecycle (basically on the fish, drops off into the substrate, then becomes free swimming to reinfect fish). If using a dye based med, vacuum & WC before redosing to help reduce the ich numbers.

Good luck
 
Just the clown loaches and tetra; rest of tank seems fine. I don't think it is ick because they are more powder like and flat; my guess right now is that it is epistylis but that is a guess.
 
Ultrastructural observation on attached Apiosoma did not reveal any interference with the host cell serving as substrate (Lom and Corliss, 1968; Lom, 1973; Fitzgerald et al., 1982) or peripheral tissue response. Thus, mortalities following massive colonisation of gills by sessilians (Fijan, 1961) could result from the dense cover of sessilians disrupting gas exchange through the respiratory epithelium. The only exception among these infections are the colonies of the stalked sessilia Heteropolaria (Epistilis) which cause lesions (“red sore”) at the stalk atachment to the fish skin, these inflamed haemorrhagic lesions are also contaminated with the bacterium Aeromonas hydrophila (Esch et al., 1976; Miller and Chapman, 1976).

I had never encountered nor heard of this problem before this post. So I went looking for the science as is my habit. The above is one piece of info I found.

In reading I discovered that this infection, on bottom dwellers tends to start on the percoral fins as they are more in contact than the substrate. Also this parasite tends to grow a bit away from the body with a tuft which often causes it to mistaken for a fungus as fishorama pointed out. Early on it can be mistaken for ich as well.

I also read that ich tends to spread all over a fish while epistylis tends to concentrate more in fewer areas.

Rodrigues, R.A., dos Santos Sanchez, M.S., Fantini, L.E., Nunes, A.L., Kasai, R.Y.D. and de Campos, C.M., 2019. Use of common salt (NaCl) in the control Epistylis sp. in hybrid sorubim. Revista Agrarian, 12(46), pp.495-502.

Abstract: Epistylis sp. is an emerging parasite in Brazil and is commonly found in surubim Pseudoplatystoma spp. during the initial stages of production and, therefore, requires the establishment of prophylactic and therapeutic measures, aiming at its control. Therefore, the present study aimed to evaluate the use of common salt to control Epistylis sp. in surubim juveniles. The fish (n = 48) were randomly divided into three treatments, and a control group, with three replicates each. The treatments consisted of three therapeutic baths performed every 48 hours for 20 minutes with different concentrations of common salt: 0.0%, 1.0%, 1.5% and 2.0%. The experiment lasted six days. Twenty-four hours after the last bath, the fish were sampled to check for the presence of the parasite and blood collection. Salt
treatments of 1.5% and 2.0% were effective in eliminating parasites in 82% and 78% of treated fish, respectively. Fish subjected to the 2.0% salt bath showed higher hematocrit and hemoglobin values (P <0.05) compared to fish in the control group, in addition to changes in leukocyte values. Common salt can be used to control Epistylis sp. in naturally infected surubim juveniles.

https://pdfs.semanticscholar.org/97cd/b05467e84c54052374ffa4ee0ec7e07709d7.pdf

I think the fish has ich from what I can see in the pic and what I have now read re Epistylis sp. However, if the salt article is accurate, then it would appear help with either ich or Epistylis.
 
BUt would you treat a clown loach with salt given their sensitivity to salt... remember i have to treat the tank as they do not want to be caught.

I had never encountered nor heard of this problem before this post. So I went looking for the science as is my habit. The above is one piece of info I found.

In reading I discovered that this infection, on bottom dwellers tends to start on the percoral fins as they are more in contact than the substrate. Also this parasite tends to grow a bit away from the body with a tuft which often causes it to mistaken for a fungus as fishorama pointed out. Early on it can be mistaken for ich as well.

I also read that ich tends to spread all over a fish while epistylis tends to concentrate more in fewer areas.

Rodrigues, R.A., dos Santos Sanchez, M.S., Fantini, L.E., Nunes, A.L., Kasai, R.Y.D. and de Campos, C.M., 2019. Use of common salt (NaCl) in the control Epistylis sp. in hybrid sorubim. Revista Agrarian, 12(46), pp.495-502.



https://pdfs.semanticscholar.org/97cd/b05467e84c54052374ffa4ee0ec7e07709d7.pdf

I think the fish has ich from what I can see in the pic and what I have now read re Epistylis sp. However, if the salt article is accurate, then it would appear help with either ich or Epistylis.
 
It would only be a temporary med. Add it slowly over a few days. If you do WCs add enough to get back to optimal dosage. When treatment is done, remove by WC over several days too
 
I said I'm not a huge salt user, I've done it a few times in 40+ years of fish keeping. Loaches are said to be scaleless but that's not really true, they're very small & imbedded in theit skin. Loaches are also said to be dye sensitive. But half dosing meds is less than half as effective & must be done at least twice as long many times. You need to continue any treatment for 7-10 days after all signs of ich (or whatever) are gone.

I haven't seen problems gradually getting to a full dose of malachite green over a day or so, say half a dose in am then another half dose in pm. Then full dosing as per instructions after that. If you choose a dye med, do WCs & vacuuming before adding another full tank dose, I think it's every other day dosing. I don't think I'd raise the temp much if at all but it can speed up the ich life cycle. With either tx you want extra aeration, leave the water level down a few inches so there's a nice splash return. & realize your tank doesn't really hold as much water as size says, it's more a ballpark. Substrate & decor can account for quite a bit of volume.

With salt it's not just the eventual dosage but also the very quick rise in TDS (total dissolved solids) & why I recommended adding it over a few days...& removing it that way too.

If you choose salt start with 1/2 teaspoon per gallon dissolved in tank or dechlorinated water, then add another 1/2 tsp tomorrow. If you do WCs (you should!) add enough to get you back to the current dosage/gallon. I "think" the salt dose is 2 teaspoons/gallon but look it up to be sure.

Your tetras & plants are not going to "like" either salt or dye. Meds are stressful to most fish. Salt is removed by several WCs; dye is removed by carbon in the filter & WCS.

Pick a tx & start NOW, your loach looks in poor shape: lots of white spots, heavy slime coat, gray color & that bent tail posture seems quite bad to me. He probably hides a lot so you may have missed the earliest signs, this seems a bit advanced.
 
Nearly all the tetras have already died. I have one cardinal left that seems unaffected (out of 20) and one glow light that seems to resist everything (I used it to cycle a tank 3 years ago). However I do have 10 zebra and 4 yoyo in the tank along with 2 angels and the 6 clowns. The tank is 120 gallon so you are talking about 60 teaspoon and then another 60 teaspoon - i just don't have that much non-idonize salt sitting around. I did add a UV so maybe that will help a little. I do have some malchite green but again not sure enough to treat a 120. The white spots have been reduced on all the clown but one that is not doing well. Tomorrow i'll do my normal 60% water change; then I'll re-evaluate adding salt. Part of the issue here is i'm not 100% sure of the disease but i've seen ick before and it is not ick.
 
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