Do I need a bigger tank?

[stillwearingaredribbon]

I have a 50L tank
I have 7 minnows and 4 shrimp. I water change (about 50%) every 7-10 days. The water stays lovely and clear but I have a lot of algae and snails

The filter was cheap and the whole bottom part is supposed to be replaced so the foam is lost. I wash it a couple of times in the tank water so don't change it so often
Do I need a better filter or a bigger tank or both?
I only have the light on a couple of hours in the morning and evening and the tank is not in direct sunlight

The answer to 'do I need a bigger tank' is always yes

50 litres is on the small side for minnows but it is just about doable. If you've got a lot of snails then it might be that you're overfeeding and/or there's a lot of detritus. Do you clean the gravel thoroughly when you do water changes? Have you tested the water? That'll tell you a lot about why the algae is happening. Usually it's down to too much nitrAte or phosphate.

When you say the foam is meant to be replaced, is it active carbon? If it's just plain sponge then you don't need to replace it until it falls to bits, despite what the instructions may tell you. Carbon does need to be replaced regularly but there's no need to use it in most tanks so you could just take it out and put a normal sponge in. If you do replace it then do half at a time so you don't lose all the good bacteria in one go.

Describe the algae.
Colour, location, texture etc.

Different types of algae signify different issues.

Green and floaty over the gravel and plants
A nice vibrant green
Some very dark, almost black in the back wall of the tank
If I stir up the gravel it floats about in clumps and I fish it out with a net

Is it like a slimy layer over everything? Sorry, I'm not good with descriptions. That would be cyanobacteria which is not really an algae. It's easy enough to remove but it can spread pretty quickly in the right conditions.

True algae is normal in an aquarium but can get out of control if the nutrient (nitrate and phosphate) levels are high. This is usually down to too much food and not enough cleaning so it should be pretty simple to sort out if what you've got is algae rather than cyanobacteria.

If you test your nitrAte and phosphate levels then that will tell you more. Tap water phosphate can be pretty high in some areas so I would test that as well.

This is a pretty good article about algae if you're interested. Wait, you're interested, right?