did a 50% water change this weekend and ive started dosing liquid easy carbo last week. I have 240lt tank and been doing 4ml a day. After the water change on Saturday the tank was looking crystal clear and I was really happy. Sunday morning every fish is at the surface gasping for air and the water has gone cloudy?
I'd contact the manufacturer with Lot # & see if they had any other reports - make sure you get someone in tech service to help rather than sales or reception, as they may be able to assist with trouble shooting.
Your experience with a product such as Easy Carbo is unexpected, that's a reasonable dose (unfortunately there are no actual specifications listed on the website but I doubt this product is significantly different than Excel)
I don't know how a "pebble" could absorb sufficient EC to affect what seems a failrly large tank (unless you have a LOT of pebbles???)
once that was all sorted I used an anti bacteria and fungal treatment to help the cardinal tetras that had suffered with the ph stress. Just lost another two tetras.
What symptoms were cardinals displaying?
Unfortunately what manufacturers don't reveal is that any
anti bacteria and fungal chemicals targeted for aquarium use will affect filter bacteria, most of these compounds will also stress fish (who are now swimming in the stuff so there's no escape) - treating fish with medication is always a balancing act between the disease related stress & chemical stress
Whenever you add meds to a tank, recommended protocol is 25 - 50% daily water change before each dose, maximize water level oxygen (eg, decrease tank temp from 25C to 23C, ensure good surface movement, allow filter returns to splash gently), don't mix chemicals (the Easy Carbo may be interacting with the med chemicals)
Most medications are not very stable under aquarium conditions so daily dosing is often the standard protocol, it's always worthwhile to look up independent information on the use of the specific compounds (in the medication) with regards to ornamental fish treatment.
If you add any sort of med & observe an adverse reaction, call the manufacturer - they should be able to suggest possible cause & guide you through some of the possibilities.
At this point - especially as fish are still dying & water has gone cloudy,
I'd stop dosing,
perform a 50% water change (use additional water conditioner - Prime is excellent in this situation as it also binds ammonia & nitrites & can relieve some fish stress),
add in carbon to remove residual medication product/by-product
If you feel you need to do something re the cloudy water, add in a UV sterilizer or ultra-micron filter - don't add any more chemicals (eg, water clarifying agents that offer to clear water by precipitating out whatever)
That pH 3 crash may've affected filter bacteria, so your tank may still be re-balancing.
If you can manage, just try doing 25% daily water changes for the next week or 2 - if you can't manage daily, try to commit to alternate day water changes - always syphon the substrate area for these rather than just removing water from the upper areas, try to cover most of the tank footprint.
Watch for signs of ich (you do want to treat this with chemicals) as this can often occur as a secondary infection given the stresses of the last month