Water change after cycle

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Darter217

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So I know that you're supposed to do a large water change once your tank is cycled. About 90%? Do you need to heat your water up before you put it into the tank during this water change? Or can you just put the cold water straight into the tank and heat up for a day before adding fish since there isn't any fish in there yet.
 
Since you've added bicarb during cycling you'll need to remove all the water down to the substrate to get rid of the bicarb.

You can refill with cold water but as tap water is pretty cold at this time of year (mine is 9 deg C) it could take a while to reheat. If you have a combi boiler you can add a mix of hot and cold but if you have a hot water cylinder with a header tank in the attic you can't (risk of contamination in the header tank). You could always add a few kettlefuls of boiling water to speed up the heating.
 
Since you've added bicarb during cycling you'll need to remove all the water down to the substrate to get rid of the bicarb.

You can refill with cold water but as tap water is pretty cold at this time of year (mine is 9 deg C) it could take a while to reheat. If you have a combi boiler you can add a mix of hot and cold but if you have a hot water cylinder with a header tank in the attic you can't (risk of contamination in the header tank). You could always add a few kettlefuls of boiling water to speed up the heating.


We have a boiler but I'd probably use the kettle method just to be on the safe side, I will be getting the tank ready a whole day before putting any fish in so I imagine it'll have time to get up to temp. I'll have it at about 25 degrees Celsius.
 
If you decide on the two barbs (in your other thread) 24 deg C would be better :)
 
If I didn't add any bicarbonate and the cycling was fast, do I still need to do a large water change?

In my case, the fishless cycling worked like this:
I let aquarium (25 gallons water in 29 gallon tank) with plants and substrate (Seachem Flourite and CaribSea Ecocomplete) sit for a couple of weeks. Tap water hardness is pretty high like 180ppm GH, 143ppm KH and aside from adding Seachem Prime water conditioner, no other treatment of the water.

A couple days before cycling, I added Seachem Flourish tabs and CaribSea Aquatics Floraspore Mychorrizal to the plant roots.

Then started:
day 0, measured 0ppm NH3 and added 3ppm NH3
day 1, measured NH3 to 3ppm or so
day 2/3 I forgot about it.
day 4, measured NH3 close to 0, Nitrite 0, and Nitrate in the 20s - certainly less than 40 (those API color cards look indistinguishable 10 vs 20)

pH measured by one of those digital pens - calibrated a few months ago but not recently - reads about 7.8.
 
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The reason for the big water change is that the cycle makes nitrate, sometimes a lot of nitrate depending how many doses of ammonia were needed, and the big water change is to get the tank water back to the same as tap water.


When a tank is planted, if there are a lot of plants, a fishless cycle with ammonia is not needed. All you need to do is wait till you are sure the plants are growing well, then get fish a few at a time. This is called a silent cycle and relies on the fact that plants take up ammonia faster than the bacteria, and in tank with a lot of fast growing plants, they take up all the ammonia made by the fish. The plants are the reason your cycle is going so quickly - and there's no nitrite.
 
+1 - As mentioned, In a newly cycled tank there's only a reason for a partial water change if/when there is high nitrates. Also as mentioned, in a well planted tank, the plants may use most (if not all) of the ammonia as their nitrogen source, so very little nitrate results. My friend Byron always uses plants as a cycle buffer and never adds bottled ammonia...but only introduces fish gradually.
And that's your key...a modest partial water change and adding only a fish or two at a time, allowing the system the stabilize and balance. Too many times in newer setups, hobbyists think their tank is 'cycled', then add too many fish at once, creating an ammonia spike that the system can't compensate for quickly enough.
 
+1 - As mentioned, In a newly cycled tank there's only a reason for a partial water change if/when there is high nitrates. Also as mentioned, in a well planted tank, the plants may use most (if not all) of the ammonia as their nitrogen source, so very little nitrate results. My friend Byron always uses plants as a cycle buffer and never adds bottled ammonia...but only introduces fish gradually.
And that's your key...a modest partial water change and adding only a fish or two at a time, allowing the system the stabilize and balance. Too many times in newer setups, hobbyists think their tank is 'cycled', then add too many fish at once, creating an ammonia spike that the system can't compensate for quickly enough.


I had to drain the tank down to the substrate as I asked bicarb soda to get my PH up as it was crashing and stalling the cycle. Although in other circumstances such a large water change wouldn't be required.
 

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