My 1st big ammonia Spike-advice please!

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Aquarium Advice Newbie
Jun 25, 2023
I've had my 55 gallon for 2 years. It's planted and massively under stocked (4 neon tetras, 4 oto) with a canister filter. Levels are always perfect as a result which allowed me to get sloppy I'm afraid.

Went out of town so put in 2 feeding blocks. One for the otos and one for the tetras. When I got home the tetra block was still huge- I kept meaning to take it out but I as a bit lazy about it -totally forgetting that rotting food is not a good idea because I'm just so used to east water levels.

Tested the water yesterday API kit
Ph 7
Ammonia 1-2ppm (on the fence about color)
Nitrites 0
Nitrates 5

I immediately added prime and did a 75% water change but the levels havent budged today, if anything they look closer to 4ppm.

I know prime only binds and doesn't remove and that sometimes waterchanges can inadvertently raise the ammonia levels so I'm just not sure what to do.

More water changes ?
Keep dosing with prime and give it a few days?

Advice appreciated. Feeling pretty guilty and annoyed at myself for dropping the ball.

If your Ph is 7.0 or lower, the ammonia reading you are getting is actually ammonium so not toxic to the fish. If the Ph is above 7.0, the toxicity raises as the Ph does so that is when you need to worry. At this point, if your Ph is still 7.0 or lower, I would remove any old food, do a little surface cleaning of the substrate to get any dissolved food particles that may be in there out of the water and let the biological filter do the rest.
If your Ph is above 7.0, using PRIME will detoxify the ammonia but only for 36-48 hours ( as per the Seachem agent I spoke with) so you will need to reapply the PRIME every 36 hours until the biological filter catches up with the load. Do the substrate cleaning and continue to test daily so that you can see when the bio filter is caught up. Also keep an eye on your nitrate level as that too should be rising. Do water changes to keep that level under 40 ppm.
That's how I would handle this. (y)
On a side note, for only a 4 day trip, I would not be concerned about feeding the fish while you are away. Just feed the fish a little heavier the week before you leave, do a water change the day before you leave and unless you have live plants, turn the lights off so the fish will be less active while you are away so they won't need food as they will be sleeping more. Also, most of those food blocks will not dissolve all that well in alkaline water so most often, not worth using. IMO :whistle:
Hi and welcome to the forum :)

Remove the remains of the feeding block (if you haven't already), then do a 75% water change and gravel clean the substrate every day until the ammonia is 0ppm.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks.

Check your tap water for ammonia, nitrite, nitrate and pH. Leave the water for 24 hours and test the pH again after 24 hours.


Vacation/ holiday feeders aren't normally necessary if you go away for a couple of weeks. Unlike mammals and birds that use most of the food they eat to keep warm, most fish take their body temperature from the surrounding water. This means any food they eat is used for movement and growth. This allows fish to go for weeks or even months without food and not die.

If you are going on a holiday, feed the fish 3-5 times a day for a few weeks before you go. This allows the fish to build up some fat reserves and they can live off that while you're away.
Do more frequent water changes and gravel cleaning when feeding more often to keep the tank clean.

Add a heap of live aquatic plants a few weeks before you go. They will help keep the water cleaner and provide the fish with something to snack on.

Increase the lighting time to 14-16 hours a day. This will encourage algae and plant growth and the fish can feed on that. Plus the algae will help keep the water cleaner while you're away. You can reduce the lighting time when you get back.

Clean the filter a day or two before you go. A clean filter is less likely to block up while you're away. Wash filter media/ materials in a bucket of aquarium water and re-use the media. Tip the bucket of dirty water on the lawn outside.

Feed the fish before you walk out the door and have a nice holiday. :)
First off, test your tapwater to ensure it is free of ammonia. Assuming it is, a water change will reduce the ammonia in your aquarium, and its a surefire to make conditions safer than relying on chemicals. Use prime as a safety gap, but your main method of control should be clean water.

Im assuming the feeding block will have been breaking up regardless of whether anything was feeding off it? In which case, even if you removed the block, there could be a significant amount of uneaten food left in the tank, probably in the substrate, so a good gravel vac would help keep down rising ammonia levels. Stop feeding the fish for a few days so they arent contributing too.

In the future, remember that fish can go quite a while without food. So unless you are going to be away a considerable amount of time, just leaving them unfed is often the best course to take. And if its too long then getting someone to feed the fish is better than a feeding block. If you are worried about overfeeding, measure out the correct amount into containers.

To give you some comfort, at your pH and a typical tropical aquarium temperature, ammonia would need to be north of 4ppm before it starts getting a threat to a fishes health. Keep on top of water changes to keep it as low as you practically can though.
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