Taking over an established tank - how do I know if it is cycled?

[anniepoos13]

Hello all... Advice gladly welcomed.

I've read through quite a few posts but can't find what I'm looking for with my specific situation.

I bought a 69 litre tank in January with two vampire shrimp and a ramshorn snail.
Tank had previously been up and running for over 2 years with these residents as well as other fish that had passed at some point.
Removed 80% of the water to transport it and filled it when I got home with tap water treated with Prime.
Has two filters, one inside and one larger one outside of the tank. These have not been changed at all, not rinsed, nothing. I was told that as the tank was already established, I wouldn't need to cycle it or change anything at all. Tested the water and all seemed fine.
Also has a heater and two air bubblers, just for reference.

After a week I introduced 2 panda corydoras, 5 neon tetras and 3 forktail male guppies.
One panda cory died the next day. Just a fluke I presume.
Two months in, one of the vampire shrimp passed from a failed moult, poor thing.
After having the tank for four months my other panda passed. I couldn't find it at all but presumed that it's tank mates ate it after it passed.
At this time I noticed that two of my forktail guppies had nibbled tails so kept an eye on the third guppy. I later noticed that he was chasing the other two and trying to nibble them. I have always fed them 6 days a week so as not to overfeed.

A week later one of my guppies passed, found part of its corpse and let the tank mates finished eating it as most of it was already gone. Two weeks later takes me to yesterday when I found another guppy dead.
Both of the nibbled ones have passed and the other one is going strong.

I tested the water yesterday, parameters look mostly good (nitrite 0, ammonia 0, ph 8.0). Nitrate is off at 50 so will do a water change.
Not sure how much to remove though.
I have never done a water change, just topped off the water every three weeks or so with tap water treated with Prime.

I only have one plant in at the moment. I had a couple more but they have been eaten by the snail.

I'm looking to get more plants and more shrimp and also to replace the fish that I lost.

A few questions that I keep reading conflicting information about:

Has my tank cycled? I presume originally so, but do I need to do anything else to ensure this?

How often should I do water changes and what percentage?

How often should I rinse/clean the filter?

What can I do about nitrates?

How should I deal with my aggressive guppy? Was that the cause of death to my other two guppies?

Thank you souch for reading this far and in advance for your advice.
Anna

 

[Aiken Drum]

You are cycled for your current amount of bioload (fish, inverts etc) if you are consistently seeing zero ammonia and nitrite in your testing. It typically takes a couple of months to cycle an aquarium. With you taking on an established aquarium, as long as you took some precautions in making sure you didn't kill off the microbial colony responsible for your cycle, you should have maintained your cycle. And then you need to add bioload (again fish etc) in a reasonable timeframe otherwise those microbes will die off due to being starved of food (ammonia) or you could lose your cycle.

There is really no such thing as being "cycled". You are cycled sufficiently for your current bioload. Once "cycled" if you add more fish your microbial colony needs time to grow to the increased bioload. If you remove fish, then the microbial colony will die off to the lower bioload. It's a dynamic thing growing and dying depending on how much bioload is in the aquarium and if you increase bioload it can take a few days to a few weeks for your cycle to catch up to this higher bioload.

From what you have said you are cycled for your current bioload.

The nitrogen cycle turns ammonia into nitrite and then nitrite into nitrate. Nitrate is the end result of the nitrogen cycle. So in most cycled aquariums you will see zero ammonia and nitrite, and nitrate steadily increases between water changes. You control nitrate to acceptable levels with your regular water changes.

You can also control nitrate by making sure you don't overfeed, making sure you don't overstock your aquarium, and keeping live plants. These measures will help you control nitrate to acceptable levels, but probably wont eliminate nitrate. There are also chemical products you can add to your filter to absorb nitrate, but if you arent overstocked, aren't overfeeding, and keep up with your water changes you shouldn't need these chemical interventions. Chemical media is a temporary measure to deal with temporary issues, and shouldn't replace you managing your aquarium properly.

50ppm nitrate is a bit high, but many people keep fish sucessfully at much higher levels than that. 40ppm is general considered an acceptable upper limit, 20ppm is a good level, 10ppm is excellent. This will come down how many fish you keep and how much aquarium maintenance you are prepared to do. If a 50% weekly water change isn't keeping nitrate below 40ppm, then consider that you may have too many fish for your aquarium size, or there may be other factors at play. Maybe you have high nitrate out of the tap which would make water changes less effective at controlling nitrate levels.

You should rinse the filter as often as you need to. Every aquarium will be different. If you notice flow getting too low, then you need to rinse the sponges, etc. This might be once a week, once or month, every 3 months. Make sure you rinse your filter media using water from your aquarium, or water treated with dechlirinator or the chlorine will kill those microbes i mentioned. You should also be maintaining your filter, cleaning down the impeller, removing any plant debris that gets trapped, rinsing out any hosing, etc. This will help keep your filter running for longer before needing replacing. Typically, every couple of months is good for a bit of filter maintenance. You may need to periodically replace parts, impeller get worn, and start rattling, so you may need to look at servicing your filter with new parts every couple of years.

Most fish can exhibit some aggression. Guppies are no exception. Social fish in small groups get stressed, and this can manifest as aggression. Larger groups of fish also spread out aggression amongst all the fish in the group, so one fish is less likely to get picked on. But fish do have a pecking order, and one fish will be at the bottom and one fish at the top. If the fish at the top is overly aggressive, and causing problems with others then it's usually best to remove the fish.

4 months without a water change is going to be a very unhealthy environment. While zero water change set ups are a thing, its not just a matter of not doing water changes, you have to set things up specifically with a view of not doing water changes and ensure you do other things instead. No water changes will result in waste building up, carbonate hardness will gradually deplete, and the topping up from evaporation causes general hardness to build up. Water changes remove harmful pathogens. You need to have a regular process of removing water, removing the contaminants that build up, and adding new clean water that also brings with it essential mineral content. Look at changing a third to half the water every week.

As you havent done a water change for so long, don't do a big water change in 1 go as that will cause a big swing in your parameters which isn't good. Start off by doing a small, 10% water change every day for a week, then look at doing a 25% changes twice a week for a couple of weeks, then 50% every week.

 

[anniepoos13]

Thank you so very much for your detailed and thorough response. There's so much conflicting information around that I honestly didn't know where to look.

I feel much more confident now and will follow your advice.

Thank you again, have a great day