Resetting up a tank

The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.

threshershark

Aquarium Advice Apprentice
Joined
Feb 27, 2025
Messages
23
Location
fl
I have a 25g tank I kept 7 orange von rio tetras, and a single angelfish, all but 3 von rio’s (transferred to a different tank) made it within a week. I got the tank from my neighbor and cleaned it about 4 times thoroughly with a vinegar and water mix, then rinsed and cleaned with water like I have done with all my other tanks and none of them have ever had this problem. I had a big decoration in the middle I also cleaned well, but my friend thinks that might be the cause of it? The decoration was also gotten from the same neighbor.

But I don’t want this huge tank to go waste, especially after all the money I put in for it, but I don’t know if I should put other fish in there (obviously after draining, recleaning, and recycling the tank) for fear the same thing might happen again.

Moreso should I get a new substrate? I currently have activflora bioactive granulated gravel in there as well as some standard black gravel to make 26 pounds, rinsing this gravel isn’t very recommended since it can kill some of the beneficial bacteria but I don’t want it to be possibly ‘infected’ with whatever killed the other fish, are my only options to rinse it or throw it away if this tank is even able to be used again?
 
There's a lot of missing information here so let's start with this: Unless the tank and it's contents was bone dry when you got it from your neighbor, anything you used from it could be an issue because whatever pathogens where in that tank at the neighbor's is still in there unless you bleached/ sterilized everything. Just washing things off is not sterilizing them.

As for the big decoration, what is it? Is it natural or artificial? Is it glass or Plastic? If it's glass, is it painted or has chipped paint on it? If it's natural, is it calcium based?

Are these Von Rios the ones that died one by one? Are you saying that the other 4 and the Angel are still alive? What are the water parameters of the water now compared to when you started the tank?

Pictures of these things will definitely help. (y)
 
There's a lot of missing information here so let's start with this: Unless the tank and it's contents was bone dry when you got it from your neighbor, anything you used from it could be an issue because whatever pathogens where in that tank at the neighbor's is still in there unless you bleached/ sterilized everything. Just washing things off is not sterilizing them.

As for the big decoration, what is it? Is it natural or artificial? Is it glass or Plastic? If it's glass, is it painted or has chipped paint on it? If it's natural, is it calcium based?

Are these Von Rios the ones that died one by one? Are you saying that the other 4 and the Angel are still alive? What are the water parameters of the water now compared to when you started the tank?

Pictures of these things will definitely help. (y)
It was bone dry yes. I read it wasn’t good to bleach fish tanks/decorations i because it could ‘poison’ the water or the fish.

As for the decoration it was artificial. I will link a photo down below of it at this moment. No other decorations were added besides live plants.

No, unfortunately four von rios and the angel all died. But yes it was one by one, the only ones still alive from this tank are three von rios.

When I added the fish the water was perfectly fine as far as tests went, I tested it twice with water in a container instead of directly from the tank and they came back with extremely high nitrate, but when I checked it directly from the tank again it was all normal. Even after the fish started dying I tested it again and it was the same.

I put a picture of the tank down below as it is right now (I am currently draining it, and deciding what to do with the substrate)
 

Attachments

  • image.jpg
    image.jpg
    101.2 KB · Views: 4
  • image.jpg
    image.jpg
    196.5 KB · Views: 4
You may have jumped the gun a bit. If the 3 Von Rios are still alive, the problem isn't the tank or the water. It may have been the way they were acclimated to the tank. It may have been that they were older and it was their time. It may have been a gender thing where the more mature males picked off the younger males. ( A one by one die off is generally a sign of this. ) As for the Angelfish, if I recall, it was a very small one and very skinny so even in the best aquarium, that fish was probably not going to make it. That's the problem with getting very small Angelfish. There is a natural die off to every spawn so you don't want any smaller than a quarter body size. So at this point, it's too far gone to know for sure the why.

Regarding the decoration, if it's hollow, it could gather detritus. If there are pockets to it, you want to make sure you have good circulation in the tank to avoid anything from gathering in those pockets. Otherwise, it looks like a cool decoration. Unless the paint is chipping, I wouldn't be concerned. (y)

As for the nitrate test, this is where there may be an issue. If your tap has nitrates, you need to use something to remove them before adding the water to the tank. Usually, when the test reagents aren't shaken enough or have gone bad, the test result should be low not high so something about the high reading is curious. I would check that out or have an external source test your water to confirm your readings.

As for resetting up the tank, I'd decide what you want to put into the tank fish wise before choosing a substrate. Not all substrates will work with all fish types. Case in point, soils that emit an ammonia or nitrate for the plants is not a good substrate for fish like Corydoras catfish or other bottom dwelling fish. So it's better to set up a tank for the fish you want vs setting up a tank and finding out it's no good for the fish you want or have. (y)
 
Bleach treating is safe if done properly. Make sure that you thoroughly rinse everything and then any residue left over should evaporate if left to air dry properly for a few days. A further safety net is that water conditioner should then neutralise any bleach left over from your rinsing and air drying.

Bleach treating is going to be more hazardous to you than the aquarium, so make sure you follow safety procedures.

A 2% bleach solution, so assuming your bleach product is 20% concentration when you buy it, then further dilute that 1/10. So if you are filling a 100 litre aquarium, fill with 90 litres of water and 10 litres of bleach. If you are dipping in a 10 litre bucket, 9 litres of water and 1 litre of bleach. Make sure you are using unscented, diluted bleach. Nothing but bleach and water. No additives, perfumes, surfacants. The really cheap janitor grade bleach.

Do all this in a well ventilated area, preferably outside.

Make sure no other chemicals are in play that might react with the bleach. Acid reacts with bleach to release chlorine gas, so thats vinegar, detergent etc. Ammonia reacts with bleach to release chloramine gas.

Leave the bleach solution in contact for 10 to 15 minutes, and then rinse thoroughly several times with fresh water. Adding a water conditioner will help further remove the bleach.

Air drying is the most important stage. Leave whatever was treated a few days in a well ventilated area to ensure all surfaces have thoroughly air dried. Any bleach residue will evaporate.

After that another rinse won't hurt anything, and when you set everything back up, a double dose of water conditioner will be your final safety net.

There are several stages of removing any traces of bleach from your aquarium and equipment and if all the stages are undertaken properly then any risk will be sufficiently managed.

You can do all this with plants too, to ensure any pest snails, eggs, algae spores etc are killed off before you add them into your aquarium. Other methods of treating plants are available though.
 
Just to punctuate Aiken's info, these are 2 of my 40 year old tanks that have been bleached many times over the year and it did not effect the sealant or the fish because I took the necessary precautions. 1742743660762.png As you can see in this pic, the fish also live in there: 1742743836726.png
 
Just to punctuate Aiken's info, these are 2 of my 40 year old tanks that have been bleached many times over the year and it did not effect the sealant or the fish because I took the necessary precautions. View attachment 391638 As you can see in this pic, the fish also live in there: View attachment 391639
Thank you both so much!

Would you suggest bleaching the tank for this situation?

And what about the substrate? Do you think I should just go ahead and rinse it anyway? I am planning to put another (healthier/bigger) angel fish in here with maybe a different type of tetra (ones that I will be getting specifically to have the proper gender balance, I definitely do not want this to happen again LOL) but they would work for this substrate. Would it be okay to use or will I have to start it over from scratch?
 
Thank you both so much!

Would you suggest bleaching the tank for this situation?
No, as I said before, I truly believe the situation was a fish situation and not a tank situation so no need to have even emptied the tank. If it was a tank situation, all the fish would have died.
And what about the substrate? Do you think I should just go ahead and rinse it anyway?
If it's still bioactively active, I'd just leave it be. If you want to take a cup or 2 and rinse it to see if there is excess detritus in it, that would better tell you what you need to do. If it's that dirty, rinse it all out and plan on cycling the tank from scratch.
I am planning to put another (healthier/bigger) angel fish in here with maybe a different type of tetra (ones that I will be getting specifically to have the proper gender balance, I definitely do not want this to happen again LOL)
There are a number of different Tetra families. Some are more fin nippers and others are better schooling fish. The more rounded species ( i.e. Von Rios, Serpaes, Black Skirts, Glow Tetras, Candy Canes, etc ) are more the fin nippers. The more elongated ones ( i.e. Rummynose, Black Neon, Cochu's Blues, Emperor, Bloodfin, etc) are less aggressive and tend to not have the same fighting issues as the others. You do want a school of about 10-12 at least to make them feel comfortable in with an Angelfish. One exception to the elongated Tetra theory is the B.A.( Buenos Aires) Tetras. They are long and extremely aggressive so they are best kept as a species only tank.
but they would work for this substrate. Would it be okay to use or will I have to start it over from scratch?
 
Back
Top Bottom