I am new to fish keeping and had the tank for only two months. My Tank size is 55 gallon and When i bought the tank i bough 10 gold fish and 2 placos with it. I do around 25% water change every week and gravel cleaning every 15 days.
It was all fine until last Saturday when i did my gravel cleaning. I removed all the decoration and washed it with tap water and then did around 40% of water change. on 4th day ( Wed Night) i saw one of the fish had a black spot on fin. I Googled it and found that it can be due to high ammonia. I don't know why because i just did water change.
on 6th day the first fish died and found other two fishes are having the same issue. I took water sample to Big Al's (From where i bought the tank and fishes), they advised me that i have high PH and HI ammonia. they advised me to do 25% water change immediately and they also sold me two liquids and advise me to follow a 7 days cycle.
Multipurpose Bio-Support Tout Usage which contains good live bacteria and have been adding it 5 ML per 5 gallon (so 55ML) add it every day for 7 days.
Amo lock which converts ammonia to nontoxic form. I was advised to add it every other days 20 ML each time so total 3 times in 7 days cycle.
They also advised me that i went too far in cleaning my tank I should not have washed the ornaments and filter as it would kill all good bacteria. I feel so bad right now that cleaning my tank is killing my fish.
It has been Three days since i am putting these products in and today my 2nd fish has died. I have noticed that three more fishes have got the black fins. Today I again did 20% water change just reduce level of ammonia from water.
I need urgent advice from someone who knows what is happening as I canít see my fishes dying.