Hi Fookie,
Look here Co2 from Aquscape Paradise. For that small tank, and long term, this could be the cheaper set. The tank can be refilled.

If you have bubblenesters like bettas and gouramis, it could be that.

Otherwise, probably a buildup of organic material combined with lack of water movement.

What size tank, what stocklist, how heavily planted is it, and most importantly, how often do you change the water, and how much?

I'd say your tank is at full bioload, which, combined with just 1 plant, means that you'll need a good water change regime.

Is the tank cycled?

You don't always do 100% water changes, right? How much do you normally change, and how frequently.

Also, does the tank have a filter?

That's true. iPhone 5 doesn't support Digi's LTE band while 5S or above can. Pity us 5 user

When I say tank bioload I'm referring to its capacity to hold fish and invertebrates.

A full bioload means the tank is at max capacity. The problem is that you've housed schooling fish in rather small groups, but thats besides the point.

Do you use dechlorinator when you cahnge the water?

I advise you to change 50% every week.

You can remove the foam with a fishnet, or scooping it up manually.

Wouldn't hurt to lower the water level - let the filter splash a bit. Creating disturbance on the water surface helps prevent foam formation.

BUNUH

Hi davlee, welcome! I started high tech tank 3 months ago.

Yes, you can have a low tech tank which doesn't use co2 (maybe just liquid carbon), that's mean you won't have a lot of choice of plants, plants will grow much slower and doesn't need a lot of light.

Wah... FOC? Where to collect?

hahahaha... yes unzan rock is really expensive. else u can opt for black lava rock. rm12/kg in penang
u r using what brand of light? aquazonic famous with ballast prob

ballast is inside the housing

i'm not using one but i've read it countless times in the previous threads...