Optimising Plant Fertiliser Dosing

Also, I've yet to find a guide that takes into account the beneficial effects of live plants in the tank.

+1 on that point...!!!  It's a shame though, as they do consider plants as virtually acting like filters, so I would imagine that having lots of plants must surely make quite a considerable difference...?

I was originally against keeping fish as I thought it cruel to contain a creature when in nature they have so much space. Then I spent a couple months scuba diving as part of reef conservation and watched fish (albeit marine) in their natural environment. And I realised that small fish don't know that they have so much space because they stay in a relatively small area. That was when I thought it might be nice to keep fish at home. So I looked to set up a micro environment. I originally wanted a south east Asian biotope, and chose plants and fish to suit. But I think that was perhaps a bit too ambitious for a newby fishkeeper, so I've gradually relaxed the boarders. Most of my fish and plants are Asian, but I've got the odd exception - Bertie my BN. But my aim is to still to create a micro environment where the fish and the plants balance each other for needs and clean up.

It took a while to find the balance, but I have since made major changes so I'm still in the process of working out what that new balance is. And it's not a static target, due to fish and plants growing, some of my fish are old aged so I am expecting deaths before I find my new sweet spot. I've not had any babies (in the tank!) yet, but that would also change the balance.

I used to think of 3 layers in the tank - top middle bottom. But since adding my fiveband barbs I've realised there is another layer, non benthic (free swimming) fish that live in the bottom third of the water column ie near the substrate but not on it. I've not yet worked out how that will affect the overall balance / aesthetic 'fullness' of the tank.

It's also worth remembering that we judge stock levels by fish length, but that isn't necessarily the best reflection of the effect a particular fish will have on the tank.

For example I have a BN Plec whose calculated size is 12cm. And kuhli loaches whose calculated size is 10cm. Their contribution to the balance in my tank is wildly different. Bertie is far more messy than his calculated stock size (even though he's an algae eater). A pair of BN Plecs is probably the most that my tank could sustain (24cm). But my kuhlis are long and thin and are more clean up crew than mess contributor. My tank could probably comfortably sustain about 15 if I didn't want any other benthic fish (150cm).

So there is a lot more to consider when finding the right stock for a particular tank than just the calculated stock %. (Which is why it is heavily emphasised that it is just a guide).

Ps @Matt I didn't read your post as a rant at all! Didn't consider it might be until you mentioned it. 

Do you mean just use the standard internal filter on the CC, @Sue  and not the oversized internal?

Under the old thinking, why does a bigger filter mean more fish? Is it purely because of the ability to hold more bacteria?

I reckon my external filter holds about 2 litres of water. Which in 220l is negligible.

If I switch to an internal filter, my current tank capacity changes from from 46% to 74%.

But, I could double the number of rasbora I have and not increase the bioload.

If I add a new shoal of small fish, then I clearly would be increasing the bioload. But would any of the bioload be 'compensated' for because I already have shoaling fish?

Yes it would. The more members of a shoal of a given species, the 'happier' they are. It is when fish are less 'happy' ie more stressed that they add more to the bioload. But that doesn't mean you can go mad and add a few hundred fish 

And it only applies to small shoaling fish.


Yes, plants do increase water quality. With enough plants you don't actually need a filter 
I live on Teesside, home to a very large chemical industry which was once almost all owned by ICI. They pioneered the use of reed beds to clean industrial waste water before it was returned to the river.

Yes, I use 'standard' internal in the CC.....

Ah, what you say Sue certainly makes sense...  Just by judging on the level of detritus/mulm in the tank, that would suggest that in my set up, I'm far closer to being fully stocked than the CC suggests - especially with the external filter option selected...!!!

With this option, CC tells me 49% stocked, although I would immediately have to allow more on the grounds of having to substitute the Corydoras (even after fiddling numbers as best as possible)...

Switching to the "Internal" filter option gives me 79% stocked and actually a much more believable & logical figure... 

This still allows me to add just a few fish though, which is nice, and in the relative confidence that this should not present a problem if any new additions are picked wisely...