I put 3 clown loaches in my tank about 3 weeks ago and this one has become very lethargic in the last 4/5 days. I'm reluctant to medicate as I've read some horror stories on the affects on loaches though the ifs recommends protozin.
Any ideas please.

he looks super thin
have you seen him eat ?
if you dont have any snails in the tank try adding some
unfortunatly i dont know much a bout laoches

Hi

Can you supply the following please so we can try to help?

Tank size in litres or gallons
Test results for Ammonia, Nitrite, Nitrate and pH
Details of all occupants (species + sizes + numbers of each)
How long the tank has been set up
When you lasted added fish or decor and what it was
How much water do you change and how often?
When was the last water change?

Thanks

200 litres
Ammonia,Nitrite Nil, Nitrate 5ppm
co2 injection on controller to 7.5
6 Platies
3 Angels
3 Siamese Flying Fox
3 Clown Loach
2 Small Plec
Tank set up 2 years, Fluval 305 external plus Fluval 3 internal for movement.
Vecton 300 uv.
Change approx 30 litres per week/10 days, changed yesterday plus external filter clean.
Most recent addition was loaches 3 weeks ago.
No new decor, live plants, rock and wood.

OK...water parameters look alright, assume that's recent test results?

But, 7.5 pH is high for some of your fish and at the very upper limit for the Clowns so may be an issue.

The other issue is that they (amd some of your other fish) are going to be too big for 200 litres.

How long have you had the Flying Foxes? And are you certain as to what they are as there are a lot of fish sold under that name erroneously, some of which are very aggressive. It's possible they are bullying your Loaches - especially with both being largely bottom-dwelling fish.

The water change schedule could do with increasing to 25% a week really.

The other thing I'm wondering about is the CO2, but I'm not experienced with it so maybe someone else can advise. It just crossed my mind that with your heavy stock level there may be insufficient oxygen in the water, especially at night (though maybe you don't have it running after lights out?).

How are the other fish in the tank generally - are they as active and colourful as you'd expect, any signs of stress in them?

Yes, recent results. I'm aware of the size issue but have already agreed with my ifs that they'll take them back before they outgrow the tank. The flying foxes have been in for about 3 months, they came from Maidenhead so I assume they know what they're talking about. There doesn't seem to be any aggression towards the loaches or any other fish.
I thought 25% weekly was a little over the top? I measure the levels regularly and they never get out of range.
As for the co2, that's a tough one. I use it because I failed to get live plants growing and used plantgrow which sent the plant growth into orbit and also choked the tank with algae. With the co2 I appear to have a balanced tank with steadily growing plants and low levels of algae.
i have to admit to being a little confused by the ph, gh and gk measurements though.
All my fish appear healthy (apart from a recent attack of cottonmouth on my Angels, qt'd, treated, now OK)
As I write the Clown has disappeared and may have already gone to fishy heaven.

Hmm, he does look in a very bad way How often do you clean the gravel?

I clean the gravel every water change and occasionally lift a rock and clean under/around. some parts of the tank are quite inaccesible due to planting but it's generally clean.

Whats the hardness of your water and what water are you using for water changes.

With nitrates that low i'd imagine RO, which would mean you may have no buffer Which would also mean you have no use for the CO2 as PH7.5 with a KH of 2 is only 2ppm Co2 when you should be between 16-32ppm.

having said all that I agree that he looks far to thin, I would say Hospital tank, feed and treat for internal parasites.

How are you regulating your CO2, and how do you know how much CO2 you are putting into the tank? Are you using a bubble counter or similar?

I wouldn't use CO2 just for dropping pH, as this will affect the fish the same as it does us humans if we have no way of dispersing it, we get CO2 poisoning. You need plants to "eat" up the CO2 or it becomes to potent. You would then need to get a lot of surface agitation to oxygenate the water which the plants would do normally, this would then release the CO2 which is then negating the reason for having the CO2. You have to be very careful when using CO2 in an aquarium as it can play havoc with a fishes respiration as well as the pH.

He does look very thin, also his fins do look a lot redder than they should be. A pH of 7.5 is way too high for loaches, they have no protecting scales and their skin is very sensitive to pH over 7.0 due to the alkalinity. How are the other two looking and behaving?

You must do 25% water changes weekly, and some like myself do 25% on some of my tanks twice a week. If you don't do the water changes regularly then you can cause stress to fish. By this I mean if you do 25% weekly you must always do 25% weekly not 9 days but weekly as in that 2 days the parametres can change and become a problem. On the tanks I do twice a week I must do twice a week without fail or the conditions will change drastically.