how frequently can i perform water changes and how much water can i remove each time?

half my fishes are suffering from severe ich infestation and i want to change the water during the treatment. the parrot fish has been idling at the corner for a few days and rubbing its side against the tank too. the oscar's mouth has been infected. 3x silver dollars covered in ich. 2x pictus catfishes have died.

One of the best ways to clear up ick is to speed up the lifespan of the parasite. You do this by increasing water temperature to around 30°C and leaving it like that for 10 days.

firstly are you sure its ich. if yes and you haven't already done so turn the temperature up to 30c. if its really bad add interpet no6 white spot cure or something similar. if its not very bad just turning the temp up may cure it. if you do add meds remove carbon if used.

its best to change the water as little as possible really but as fish keepers thats not going to happen. most people will consider once a wk 30% the norm but I have in the past done twice a wk 30% changes. if you really do need to change more than this I would consider a larger tank or removing some fish. if your having major problems with ammonia,nitrite poisoning 50% every other day would be recommended but this is to save the fish not as a maintenance program that would go on and on.

so I would say look to change 30% a wk, heat new water and treat for chlorine. you will have best results with this type of program. if you cant heat new water add it very slowly to prevent temperature changes.

sorry to hear that you have trouble with your fishes.
water change should be done regularly, without testing
kit,50% every other day. one should not wait to have
problem before doing it. when you have testing kit, water
change should be done as need arise (when there is spike
in ammonia, nitrite, and nitrate)

if you are under treatment today, you have to follow treatment
instruction, otherwise, it will be useless.

When you treat with medication, it often depletes some oxygen. It is advisable not to treat during the period you raise the temperature because warm water also contains less oxygen. If you've got some kind of air Stone, I would advise you to run it

I know interpet no6 says to turn up temp 26c and add salt.

yeah, salt plays important role too in medication:
it soften the water and enhance oxygenation. adding
medicine sometimes depleted the oxygen in the tank,
the very reason why water aggitation is required.

Temperature is currently 80 degrees fahrenheit.. approx 26 degrees celsius. I can't seem to find any website that sells no.6 and ships to USA.

Tank status:

2x pictus catfishes died
1x parrot cichlid died

2 out of 6 silver dollars covered completely in white spots
2 oscars going strong (or so it seems)


I made a 15% partial water change today and added my current ich treatment bottle. I chose not to repurchase the dead catfishes and parrot until the tank is stabilized.

just want to find out how are your oscars doing today?
are the SD responded with your medication?

Hi Paul,

The oscars seem to be fine.. the ich has not gotten to them.

However, I don't know how effective the ich medication has been. One silver dollar died today.

Also I seem to have difficulties operating the heater. There's a tiny knob at the top--but not sure how to increase the temperature. In regards to adding salt, how much salt is required for a 150 US gallon tank?

sorry about another casualty.
heater usually has thermostat knob, turn up to
increase temperature, turn down to reduce. pls
check the arrow sign as your guide.

for salt application, 1 tablespoon for every 25
gallon of water (other is using 100 grams per
10 gal of water) without scaleless fish.

do you have carbon in your filter machine? if so,
it will just remove your medicine in the tank.

I haven't removed the carbon--maybe that is why

I did the 3rd water change of the week, and siphoned the rest of the dirty gravel. I was also finally able to create aeration/bubbles from the water that enters back into the tank from the filtration system. Woohoo! Previously the tank had solely relied on air stones to aerate the tank. I will perform a water test tomorrow to test the waters. Two days ago the nitrate was orange colored (~20ppm).