What is worse? Nitrates or Temperature change.


Not sure what to do here. It has been so hot around here that I can not get my tap water below 85 degrees. I keep my tank at between 72 - 75 degrees. I have not been able to do water changes because I can not get the water anywhere close to the tank water. My nitrates are building and I need to do a water change but I don't want to send my fish into shock. I do not currently have access to any 5 gallon buckets (at least not enough to change enough water) What should I be more worried about the nitrates building for the short term or should I go ahead with the water change with the higher water temp?

I know neither is a great option but just wondering which is the better of the two evils.


Hmm..... Both are bad. I think that temperature change is survivable... Ill have to go with NitrAtes at worse...


I would believe nitrates are worse... The water will cool.


You could freeze bottles of water and add them to the tank as you replace the water. What is your nitrate reading?


Or just dissolve some ice cubes in your tap water. Four or five per gallon should lower the temp enough to use in your tank.


Do you have a nitrate reading?

In my opinion, in the short term a large temperature swing is a lot more likely to harm fish than slightly high nitrate.

I take it you do water changes with a python or similar. I've not used one, so I don't know how they work, but can the water flow be turned way down to a trickle? If you do want to do a wc, you could drip in the new water very slowly so that the fish are not shocked. Maybe drop in some ice cubes as others have suggested. Fact is, in the wild fish are subject to large temperature changes all the time. You just don't want to shock the fish by a very sudden change since they're used to a steady certain temp.


I don;t understand...you don't have cold water?


If your nitrates are not getting excessive, I suggest doing small daily water changes instead of one large change. And, when returning the water, do it very slowly. A 10 degree increase in temperature might cause your fish some stress.


why don't you just fill up a bucket of water an hour before you change your water?


I have been battling this the last couple months. My "cold" tap water comes out around 90-92 here in the AZ desert. What I do is I have a 5 gallon jug I fill twice to do a 10 gallon change/week in my 29 gallon tank. I fill that 5 gallon jug with a half gallon pitcher. I fill the jug about a third of the way, then fill the pitcher and leave it in the freezer a while. 30-45 minutes. Then fill it another third, and do another pitcher of water in the freezer. This one gallon of freezer treated water usually cools the 5 gallons to 80 or so equaling the aquarium temp. It considerably lengthens my water change time, and I have to keep my filter full in the mean time.

This is obviously not ideal, but it is what I feel I have to do to maintain a healthy tank.

I do not drain any water until the first 5 gallons is ready, but it is a couple hours after that until my water change is complete.

I can't wait for the fall and cooler temps


the OP is in delaware.... I can understand if it were out in the dessert.


Good morning,

Both high nitrates and sudden temperature changes can be harmful to your fish.

I would recommend using a 5 gallon bucket and let the water set over night. Add an air stone for circulation. Check the temperature the next morning. See if it is anywhere close to what the temperature in the aquarium is.

Any bucket will work 2g's, 5g's. Just make sure the bucket has never seen SOAP!



I would go with smaller water changes, If you tank is only about 10 degrees diff I would just keep doing smaller changes so that the fish don't notice the large swing in temp.


Thank you for all of the responses. Because of weeks of 90+ Degree weather our ground is so warm and our water lines are so shallow it has heated everyone's water. Good news is I can turn on only the cold water and take a shower. LOL saves money on the hot water tank.
I have been doing about 5 - 10% water changes everyday instead of the normal weekly 25 - 50% and everything appears okay. The water mixing with the water in the tank looks like it is only causing about a 2 or 3 degree rise and quickly settles back to normal.
It is finally cooling off around here so hopefully I can return to my normal routine soon.
Thank you again for all of the help.


You have some large waste producing fish the 46g tank so I would imagine the Nitrates would build up fast. All of them prefer a little warmer water so 85F is no big deal in the short term. 80f would be good as a normal temp after the weather cools.

I would suggest doing small water changes everyday and keep those Nitrates down. The Clown Loaches especially are very sensitive to water quality.


oh wow.

How about you chill a gallon of water in the refrigerator and mix it in a 5 gallon bucket with the warm cold water until you get the temp you want?

You should get at least one 5 gallon bucket. They are really useful.


Another thought I had.....

Why not run the tank around 84F? Then you are working with water that is close enough in temp that you don't have to worry about it.

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