Water Change Impact on a Cycled Tank

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nzafi

Goliath Tigerfish
MFK Member
Mar 14, 2008
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I was wondering what everyone's thoughts are on the impact of large water changes on a cycled tank. I am in the scenario where I will be moving my 75 gallon tank which requires me to drain the entire tank. My plan was to drain the tank and then fill it with new water. I have an FX 5, which I would leave filled and connect that to the new tank. My hope would be to still have a fully cycled tank as fish need to go into asap.

Guess my concern is that if I drain 100% of the water, wouldn't that kill the bacteria in the gravel/substrate, and then wouldn't it also destroy the bacteria that is in the filter?

I was thinking of buying several buckets and then trying to save around 20-25 gallons of the water.

Thoughts?
 
It shouldn't be an issue at all. I've done it several times with no adverse side effects. Just make sure you use a double dose of dechlorinator. How long will the filter not be running?


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My plan is move the tank, refill it and then get the filter running again asap. I suspect it will not be running for about 3hrs to 4hrs max. I am literally moving the tank a couple feet so its more just draining, moving quickly and then refilling.
 
Should be fine, check your water parameters afterwards and if you do happen to have a re-cycle make sure to do a small water change every day until your perameters are in check.
 
bassguy said:
100% is hard on the fish and bio.
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he said he wasn't going to drain the fx5 to me that's all that matters. He could even fill up a bucket with tank water and hook up the fx5 to that while he's moving the tank. no worries at all then. Fish should be fine as well, I've had to move a 125g and 100g several times over the past few years. No adverse affects.
 
I filled a large cooler with tank water hooked up back up heater and the filter, placed fish in there like a temp tank, place all deco in buckets with tank water and air stone, drain rest of tank and move tank, filled 75% with airstone from bucket and heater runnin and dechlorinate, added deco and hooked up filter back in tank while dripping fish in the cooler add fish top off and test parameters mine came up clear but I still had a small cycle (haze) next couple days I let it do its thing and it cleared, follow normal routine after...
 
I just did this and completely screwed my cycle!!

I removed 80% of the water, enough so I could drag the tank to where i wanted it, then i put enough prime in for a triple dose on my size tank (600L) then i refilled the tank, after about 2 hours my water went like milk, my ammonia test was through the roof and my cycle was destroyed!

PRIME DOES NOT WORK FAST ENOUGH TO SUPPORT LARGE WATER CHANGE!!!

If i was you i would try and get a drum and keep your existing tank water, OR dis connect your existing filter, or turn it off, app prime, refill the tank, add use a powerhead to mix the water for at least 1-2 hours!! then reconnect your filter!
 
yogurt_21 said:
he said he wasn't going to drain the fx5 to me that's all that matters. He could even fill up a bucket with tank water and hook up the fx5 to that while he's moving the tank. no worries at all then. Fish should be fine as well, I've had to move a 125g and 100g several times over the past few years. No adverse affects.
Click to expand...
the bacteria in the canister will be fine for at lease 6-8 hours with no running water!
 
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