Stocking A 64litre

Hi there,

Was wondering if anyone could advise me on the stocking limits of my tank, I seem to be reading a lot of conflicting information and don't want to risk overstocking.

I have a 64litre running since the end of December, internal filter, planted with an assortment of plants. Currently housing my 6 penguin tetras.  Levels are pH 7.4 ammonia 0 nitrite 0 nitrate 30 temp 24c. Am on a routine of weekly water changes of about 12litres.

My long term plan is to have some neon tetras but I know I need to wait a while for these until things are better established.  My question is whether I can add any others or would the penguins and neons have me stocked enough?

Thanks in advance and excuse the poor photography but thought I'd add a picture anyway

pH 7.4 would seem rather high to suit wild caught Cardinals, particularly as it's likely that hardness will be quite high as well.

I've got 7 diamond-head neon tetras and they seem to be happy and healthy in a pH of 7.4. I use RO water in with my SE England hard water to keep the GH at 10° and the temp at 22°C. However, the neons are almost certainly tank bred.

Unless you plan to soften the water then neons may not be the best choice. Black neons (here) are reputedly far better for harder water.

Here's a good article In Praise Of Hard Water