advice needed

[hoppinghippo]

I have some qns:

1) what is the optimum wattage for a 20 gallon tank? (if plants like riccia are to be grown)
2) if external filter is used, what happens at nite? as in externel filter is useful in the day cuz it doesn't aerate the water hence co2 is maintained but I"m wondering about the nite when co2 levels increase, will the lack of aeration cuz co2 to rise to unacceptable levels?

I"m currently using one of those common top filters and a 36W PL lamp for my 2 ft tank. thinking of upgrading to external filter and maybe 72W. thanx for your advice!

[tawauboy]

don't think there is really an optimum wattage.
2-4W per gallon seems to be a common guideline, depending on type of plants and depth of tank.

never planted ricca but seems that ricca need a lot of light.
so may be above 3W per gallon.
around 60-80W should be sufficient.

at night, as long as there is no co2 injection, there should be no problems with co2 poisoning.
just set the co2 injection timing to be same as light on timing.

top filter, i pressume it to be a overflow filter.
not good as it causes surface turbulance, therefore co2 loss.

hope this helps.

[hoppinghippo]

thanx for replying!

Anybody know the cheapest place to buy riccia?

[sherchoo]

Light - Since you're having 36W PL it's a good idea to add another 36W PL esp if you're gonna grow Riccia. Should be sufficient.

External filter - it will have little or no effect on co2. It does not really aerate the water, but more like to circulate the water. Just make sure you stop injection at night (when the light turn off). During the day, the water should be well oxygenated enough to last thru the night for the fishes.