New Tank- Time for 100% Water Change?

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CharlesLeeRay

Aquarium Advice Newbie
Joined
Oct 21, 2016
Messages
4
I am having a myriad of issues cycling / starting my new tank.

Here's a short summary.

125 gallon freshwater.
2 Aqcua Clear 400 GPH power filters
Undergravel filter
Moon sand
Originally had live plants. Have moved to just all artificial now.
Running for 6 weeks now

Ran for a few weeks fishless after setting up. After a few weeks added 2 common goldfish to help cycle. Both did fine for a week. Tank then underwent a bacteria bloom, got super cloudy and both died. Levels all spiked and remained high for a few weeks, never coming down, so decided to add API quick start. Levels all dropped to normal within days.

After tank had been set up for 4 weeks I continued treating with API quick start to keep levels normal, and added 3 silver dollars. Both developed red gills and fin rot and died within 2 days. Thinking tank still might not be cycled I waited another week and then added 10 Zebra Danio's since they are hardier. All died within 2 days after developing fin rot and red gills.

Let the tank sit another few weeks and tested water levels again. Everything was normal. This time added 2 goldfish again. Both did ok for a week, then seemed to develop white growth like bumps on them and redish gills; obviously both died.

So... at this point I am done killing fish. I clearly have a problem with my water and will not add anymore until this gets figured out.

My question for you is this: Is the likely cause of my problem that my tank is simply still not cycled after 6 weeks, or that I have a bacteria or fungal infection in my tank that needs to be treated?

Should I treat with medication for a week and then do a large (75-100%) water change since there are no fish or plants in it to worry about dying? Or do I just medicate and do small (10-20%) changes? Or do I not medicate and stop adding stuff to the water and just let it run for a few more weeks?

HELP!!
 
If there are no fish in the tank, change out all the water. That will lower the amount of toxins or pathogens in the tank. I would do it even if there were fish in the tank, leaving only enough water to cover the fish.
If you have a sand substrate, you can't use an under gravel filter.
 
125 gallon tank!

That is huge. This is what I would do;; start from scratch; put new water and let tank cycle on its own. Don't add fish or chemicals. I don't like chemicals. Check ammonia levels after 7 dayz or so; if ok add fish slowly.

Mike.
 
Ya I had one from a previous tank so decided to use it just for the heck of it, not realizing it would be worthless with sand. But I guess a question to ask, could it actually be doing me harm? I just figured it's probably doing nothing, but could it actually be hurting the water quality?
 
are you using water conditioner?
is your tank going to be for cool water fish or tropical fish?
 
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