How do you calculate the maximum number for fish per gallon?

[aquamist666]

How do you calculate the maximum number for fish per gallon, if your intention is to limit the amount of water changes to no more than one water change (20%) per month? And will adding a lot of filters with ceramic media and zeolite help as well?

 

[Fishfur]

How do you calculate the maximum number for fish per gallon, if your intention is to limit the amount of water changes to no more than one water change (20%) per month? And will adding a lot of filters with ceramic media and zeolite help as well?

You don’t. There’s no such thing because it would be different for every species.

But if the idea is to limit water changes to near nothing, which always strikes me as a really bad idea, then erring on the side of far fewer fish rather than more is the best plan.

 

[aquamist666]

You don’t. There’s no such thing because it would be different for every species.

But if the idea is to limit water changes to near nothing, which always strikes me as a really bad idea, then erring on the side of far fewer fish rather than more is the best plan.

So if my tank is 60 gallons, can I keep five platys and four corydoras and just do one 20% water change per month? I will also add a lot of plants to the tank. I'll also add zeolite to the filters.

 

[A201]

The age old question.

- species kept & number
- filtration
- food type & amount fed daily
- Planted or Un-Planted
- Substrate, gravel, sand dirt
- Substrate depth

A deep substrate, heavily planted tank w/ a small group of Nano fish might work for you.

I change out 30% - 50% of water weekly. Been doing so for ages. Really no big deal.

 

[Fishfur]

So if my tank is 60 gallons, can I keep five platys and four corydoras and just do one 20% water change per month? I will also add a lot of plants to the tank. I'll also add zeolite to the filters.

Sure, but it really won’t be in the best interests of the fish.

Cory cats like soft water. Platies need very hard water.

Many keep both together and it may not seem to bother the catfish but it does - it takes a toll on them - their kidneys are adversely affected if nothing else, because it’s more work for them as the fish tries to osmoregulate in harder water.

Soft water species manage adaptation (to a degree) to harder water far better than hard water species can adapt to softer water.

Doing only a 20% water change per month won’t replenish the minerals or buffers that get used up.

Plants will certainly help take up some of the dissolved organics but they can’t replenish used up minerals or buffers.

You risk having the KH crash, which will crash the pH and the Platies will not fare well if that happens. GH may also drop too low for the Platies as time goes by.

 

[Whitewolf]

Changing the water is part of the hobby. Why are you limiting it to once a month? It gets easier i actually enjoy it. I do mine like once or twice a week and I have 20 aquariums

 

[Mudminnow]

If you have a filter that holds enough beneficial bacteria to keep ammonia and nitrite at 0, then adding more filtration doesn't really do anything. The available space for the bacteria isn't the limiting factor for their growth, it's the amount of food they have available. Put another way, nitrates would still build up at the same rate whether you had just enough filtration or way more than necessary.

Yet, there are plenty of examples out there of healthy aquariums that receive few to no water changes.

Here's one:

.

All such tanks that I've seen are heavily planted (like nearly 100% of substrate is planted) with hardy, adaptable plants. That is, they pretty much look like the one in the video above.

My guess is that it would take a lot of close observation along with trial and error to get right.

 

[SparkyJones]

I don't recommend 20% water change per month only for the next forever. If you do decide to go that route use RODI water and adjust it as needed for the plants and fish you keep. By doing thar you won't be accumulating while topping off for evaporation and you won't be depleting over time either.

I know people are going to sat "no water changes!" but other things are done in order to refresh nutrients, and stave off concentration of lesser used nutrients and keep it in balance.

In example a heavy planted tank will eat up nitrates nitrites and ammonia what it won't do is add enough nutrients to keep that going without adding to it. You add fish to add waste that will break down into nutrients but too much and you start to polute.
All the while water is evaporating, and you'll be topping off. If using tap water, it's coming with nutrients built into it. Add, evaporate, add evaporate, soon enough it's building up on you which is why you'd need the plants. If one nutrient depletes, the plants won't do well and if too much the fish won't do well so it's all about keeping a balance.

Hope that makes sense. Honestly it's just easier to water change.

"No or small water changes" doesn't exist just like fish living long lives In a puddle don't work either unless it keeps on raining.

You can do no water change or minimal water changes but you'd need to take measures that maintain the right balance. Slacking at some point will lead to failure.

 

[bgarthe]

How about a compromise suggestion……
1. Yes, fewer fish will lessen need for frequency and % WC.
2. Consider doing 35% WCs every 3 weeks…….in other words, make your “month” a bit shorter and your % s a bit bigger.
3. Either match your fish to the water hardness you have or change the water hardness to match the fish you want.
4. All while doing this, monitor your Nitrate levels. Watching nitrate levels is a good indicator/way to keep track of the water situation telling you when the need is there to do a WC. Use a good liquid test, not the strips for this…..and……remember to shake the $*&@ out of bottle #2 of the API NO3 test kit if that is the one you end up with.

Finally…….remember…..doing any WCs is always better than doing none.

 

[KingOscar]

Of course fish bioload matters.

I've done 40-50% water change every two weeks for years. Light to moderate fish load, no plants. My fish are healthy and regularly meet or exceed their expected lifespan.

It always struck me as curious that while all proficient fish keepers recognize that a heavy load requires more water changes, fewer seem to note that a light load requires less. For some reason there's this idea that every tank needs weekly water changes. They don't.

 

[A201]

I've seen countless videos and pics on line depicting successful no maintenance, self sustaining aquariums.

I'm not doubting the authenticity of the setups, but maybe the aesthetics of them. Most of those tanks look "swampy" and simply sloppy.

To each their own, but I like to incorporate a natural look to my tanks, coupled with a tidyness only accomplished by sensible regular tank maintenance.

 

[TClare]

Just to add to all of the above, if you start with 5 platies and they include males and females you will soon have a lot more!