We’ve all read up on certain fish, inverts, corals, plants etc and seen something along the lines of “they need a well established aquarium”, but at what point can you class your aquarium as well established?

Young Tanks (0 – 4 Months)

Young tanks are tanks that have just completed their nitrogen cycle, even after your tank is “cycled” you are likely to see swings in your waters parameters such as slight ammonia spikes, nitrite spikes, algae growth (including pest algae), calcium and phosphate swings and many other slight changes in parameters.

Yellow Snakeskin Male Guppy
Yellow Snakeskin Male Guppy

The swings in you waters chemistry will effect certain livestock more than others, there are certain fish, corals, inverts etc that need stability, which will only come with time as your aquarium matures. Young tanks are more susceptible to chemistry swings and they are more likely to experience pest algae which consume certain minerals within your water, which can result in false readings from your test kits as it is actually the algae that is absorbing the nutrients that you are trying to detect within your tank.

When your tank is in the Young Tank stage, you are best to stick with fish & livestock that are known for being a bit more hardy & resilient to tank swings.

Young Tank Stocking Examples

Saltwater ExamplesFreshwater Examples
Royal GrammaGuppies
Ocellaris ClownfishZebra Danio
Firefish GobyPattys
Trochus SnailMollies
Hermit CrabRams-horn Snails

Semi-Established (4 – 8 Months)

At 4 to 8 months old your tank should have settled down and started to find the parameters it is happy to run at. Some of the parameters may not be what you are looking for so you might consider dosing at this point.

Hopefully by this point you should be starting to get a hold of any pest algae, and have added the relevant cleanup crews to ensure it doesn’t take a hold! But you should still have algae, enough to feed certain livestock.

Watchman Goby
Watchman Goby

You should have mastered the art of water changes & water testing by now and should be confident that your parameters are becoming stable. You can now consider livestock that is classed as moderate care level.

At this point pytoplankton, algae spores, copepods and other nutritional, tasty goodies will have started to establish themselves, so you can consider adding some of the more hardy filter feeders to your system.

Semi-Established Stocking Examples

Saltwater ExamplesFreshwater Examples
Carberryi AnthiaCherry Shrimp
Sand Sifting GobiesApistogramma
BlenniesRed Tailed Shark
Feather DusterKribensis
Soft & Easy LPS CoralsBamboo Shrimp

Well Established Aquariums (8 – 15 Months)

Through the ups and the downs, you should now now have stable water parameters, a good variety of algae (that’s not taking over your tank) and you should have mastered the art of keeping water… I mean fish… no, I mean water!

The art of aquarium keeping is not really about fish, it’s about keeping water. Keeping it clean, keeping it stable, keeping it at the right temperature & salinity (for reefers that is). Once you have mastered this and are happy that you current inhabitants are happy, healthy and thriving you can consider moving up another notch in the fish keeping world.

For salties, this would be the time to think about adding that Mandarin you have been cooing over, or the Anemones you have always wanted for your clowns. For freshies, go buy your Discus fish, Electric Blue Rams or Angel fish… You have made it! (Be sure to research any stocking purchases and ensure you are able to provide adequate care for any livestock)

Your tank inhabitants are thriving, you know the level of commitment required to keep your aquarium at a high standard and you are prepared to put more time in to keep that dream fish.

As a bit of a disclaimer, I am not saying that at 8 month old your tank is ready for anything, this is just a guideline I have put together from my own experience with fish keeping. Your tanks stability will vary, no two tanks are the same! Be sensible about it and ask advise from a professional if you are unsure on something. Please do your research before making any purchases!

Well Established Stocking Examples

Saltwater ExamplesFreshwater Examples
Anemones Rams
Surgeonfish (Tangs)Angel Fish
SPS & LPS CoralsPlecostomus
Moorish IdolBala Shark


This website is expensive to run in both monetary value and time. If you like what you see, and find this site helpful, please consider donating towards the running costs of the site.