Ok so i bought this small Nano Tank a while ago (20 litres) after i had to get rid of my big tank because of my job. so not really had much in the tank except some endlers,rasbora and octo.
So for my birthday my partner got me a gift card for some fish. and while i know the tank is rather small it has plenty of hiding places so i decided on a male female ram pair. they went into the tank yesterday and bar a bit of stress on them from the move they both seemed fine they settled down and after a couple hours had established their territory (they claimed the log) and were eating and back to colour. but today the male ram has gone very very pale, he's still eating and swimming around but his colour has really gone down. the female is fine though, and so are all my other fish.
20 litre cube temp between 24 - 27 degrees celcius ph 7 (i use prefiltered, dehlorinated water)
Endler livebearers x 6 Otto's x 4 galaxy rasbora X 3 Lampeyes x 2
Picture attached, Please escuse the bits just did a water change to see if that helped.
So I think I know what the problem is I've just been watching him over the past hour, his colour has come back but he is acting aggressively to the side of the tank, I think he can see his reflection, is there anyway I can hide his reflection?
I'm sorry to be the bearer of bad news but a 20-litre tank isn't suitable for any fish - it's only suitable for shrimps and snails or aquascaping.
Take a look at the fish profiles for each of your fish on www.seriouslyfish.com and you'll see what the requirements are for each of the species you have in terms of tank size and volume, minimum number of fish, water parameters (eg water hardness), temperature, feeding, etc, etc. From that, you'll see that the minimum size of tank you'd need would be one with a 'footprint' of 60x30cm and 3x the water volume you have, but even then it would be overstocked with the number of fish you have.
So, even if you do manage to find a way to minimise the reflection problem, it's almost inevitable that you're going to encounter further problems (recurrent, chronic or multiple different ones) as the fish won't have their needs met.
The best advice I can give is to upgrade their tank to a size in line with their requirements and the number of fish you have - taking into account the minimum shoal size recommended for some of the species (eg ottos, galaxy rasboras, lampeyes) and which would require adding to their shoals +/- returning the ram pair to the shop and explaining that you hadn't appreciated the tank size required for them and that you're already currently overstocked.
If it's any "consolation", the larger the tank, the less work it actually requires as the water quality is less prone to daily fluctuations and therefore requiring daily water test readings - so, once established, a weekly tank clean should suffice (provided that your ammonia and nitrite levels remain at 0 and your nitrates under 20 ppm).