Turning off filter at night?

Bad idea.

Simply add CO2.
Also, no circulation is terrible for CO2 levels, the still water areas around the leaves gets very depleted of CO2.
Then it gets depeleted of nutrients.

Then the plants don't grow fast/well.

Then the nutrients produced by the fish don't get converted to NO3 or used quickly to remove the NH4.

If there's only a few plants, there might be enough CO2 to have them surbvive produced by the fish, but if a typical planted tank, there's no way for this to happen. You need too much CO2 for the plants and you'd have to add way too many fish to have the plants grow well without algae appearing. She's at a pretty low light level but I've done less, 110w on a 75 is what's saving her at the moment.
See how long it last till she gets GW. Most folks feed their Discus too much, LFS often under feed their fish. All the food will turn to NH4 first.
No filter, no CO2 and lots of light will give you algae.
She might do it for awhile, but eventually that's a tank waiting for a bloom.

As far as hurting the fish, what do think the O2 levels are?
Now have you seen a nice pearling plant tank? What do think the O2 levels are in there?
I promise they are 2x or more than hers.
I have no issue with Discus and 81-82F, 73 is too low. Ask anyone that's kept them or bred them.
They will likely go off the handle

I think with a smaller bioload of fish(How many Discus in this tank?2?) you can get away with tanks like this, but the plants will do much better if you add the CO2 and filtration, and if the plants do well.........so do the fish.

Cooler temps will hold more gas, O2 and CO2 etc than warmer water etc at equilibrium with air. Some floating plants and other plant choices can make a tank like hers work better, but I'd never keep Discus in such a tank nor recommend it either.

Regards,
Tom Barr

Originally posted by Skittyfish
....... Would it not possibly cause an outbreak of ICH if the daytime Temp is around 78 and the nighttime temp drops to close to 73 degrees?

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Sudden temp changes may cause an Ich outbreak. Discus need from about 85 to 88 degrees in water temp....

I can say this: Discus do NOT NEED a temp of 85 to 88 degrees. This is recommended by Discus zealots (As opposed to a plant zealot but certainly not needed. But the issue of of mid low 70's for extended periods or large fluxes is not good generally for most Discus aquariums, that's stretching it too far IMO, but occurances in nature are often time quite large. They are cichlids and are not as wimpy as folks like to say.

What happens when there's a large thunderstorm during the rainy season?
The water temp will drop about 10 degree F.
I've kept Discus for years at 81-82F, they even bred etc at this temp and the fry did fine. So something must be right. Maybe all the O2 is the reason they do so well, I never treated my fish once, I sold off all the fry and fish, made quite a bit of $ on the side. I don't really like colored dinner plates though so I got rid of them.


Regards,
Tom Barr

Skippy, was that just a typo? The only rock I can think of that would drop your pH is iron pyrites: they dissolve in water and give off H2SO4. Not recommended of course.

plantbrain's right: freshwater goes through daily temperature variations and freshwater organisms are attuned to them (not like reef organisms). "Night is the winter of the tropics"--was that in Adrian Forsyth and Ken Miyata's modern classic, Tropical Nature: life and death in the rain forests of Central and South America? Good to remember.

Our unnaturally stable temperatures also tend to foster bacterial cultures exactly suited to the unchanging conditions. (Not my original idea either.)

Shocks of various kinds incur stress. Stress lowers cortisol levels and reduces immunity. Stressed fish are more open to many pathogens. But Ich is caused by Ichthyophthirius multifiliis not by a cool morning.

Originally posted by wetmanNY

plantbrain's right: freshwater goes through daily temperature variations and freshwater organisms are attuned to them Stressed fish are more open to many pathogens. But Ich is caused by Ichthyophthirius multifiliis not by a cool morning.

Click to expand...

Exactly! Ich is caused by stress, such as sudden temp changes by not paying attention to differing water temps when doing water changes...
A thunderstorm is not enough of a temp change to stress fish. The temp change is minimal and At The Surface. I'm staying on the safe side and keep my Discus happy with warm temps of 85 to 88 degrees.