Is borax harmful to fish?

apastuszak

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Jun 2, 2015
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It seems an ant colony has taken a liking to my aquarium.

I have an old 55 gallon Oceanic aquarium that has a very wide glass brace down the center. On it, I have 2 glass canopies and a 48" twin tube strip light. I came over to feed the tank, and I see a ton of ants between the glass canopy and glass brace. So, I opened the lid and swept them in the tank for a quick snack for the fish.

Now the goal here is to kill the colony, so they don't keep coming in my house. And the best product I have ever used for that is Terro Ant Bait. You set one down and leave it alone for about a week. The ants eat the Terro and take it back to the nest. In about 2 weeks, no more ants. You just have to deal with an increase in ants for about 3-4 days as the colony has decided it's found an awesome food source and send all the workers out to go get it.

The main ingredient in Terro is borax. It's basically sugar water mixed with borax, and is not toxic to your pets and kids. So, I put an ant bait out on top of the aquarium and the ants have already figured out what it is and are forming a line to go get the stuff.

I can't find any info on whether borax is toxic to fish. I don't expect any problems, with a glass canopy covering the tanks and all. But you never know when a cat may knock it over and a few drops fall into the tank.

Google has been of little help.

Obviously, if I see the Terro spilled, I can do a water change. But it may take me hours to figure out the stuff has been spilled.

Anyone know what affect borax may have on aquarium fish and plants.

And, yes, I tried to put the Terro off to the side of the aquarium and the ants didn't notice it.

I feel the need to buy some archer fish now...
 
Ok, so if you do a Google search on "Borax Aquarium" instead of "Borax Fish," you learn that Borax is used in the reefkeepnig hobby to raise and buffer pH.

So,. it appears if any got in my tank, my pH would go up, something that can be remedied with a quick water change.

I'm a little less nervous now that I know that other fishkeepers have actually added it to an aquarium before.
 
That's good to know!

I'm pretty sure we used borax to clean 5 gallon buckets that we then used to store fish for an experiment in my field ecology course. We didn't lose any fish, so I would think it would be ok if small amounts were in the tank.
 
Borax (sodium tetraborate) is a common ingredient in pH buffers and some trace element mixes.

In small doses it is not harmful.
 
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