Hi all,
My main concern is oxygen levels at night when the plants will be competing with the fish.
I don't use CO2, so I like to run a venturi on my external/internal filter, or if I have a spray bar make sure that it causes some surface ripple.
I also have 2 filters (usually an Aquaball or Maxijet power-head & sponge, as well as an external) on all tanks bigger than ~60 litres.
I have a sponge pre-filter on my intake, which I clean regularly and I don't have anything like floss or fine (PPI30) sponge, that might clog and impede flow in the filter body. I have Eheim "coco-pops", sintered glass rings, PPI10 sponge, floating cell media, hydroleca or alfagrog in the filter, and no more than 2/3 full.
Some CO2 users have an air pump time switched to come on immediately the lights go off, aimed at adding oxygen and out-gassing any residual CO2.
Generally plants and fish death is another area where a lot of comments made come from people who are understandably upset, but don't fully understand what has happened.
If you have a planted tank and suffer from fish death due to low oxygen it will always happen
- at night (no oxygen production from photosynthesis, and the plants respiring, make them net oxygen consumers)
- often in the summer when the tank is warmer than normal (gases are less soluble at higher temperatures)
- and often when we have had a sudden drop in atmospheric pressure (gases are less soluble at lower atmospheric pressure).
The simple conclusion is that the plants have used the oxygen, and this has caused fish death, and this is true, but the fact people are missing is that if they
hadn't had the plants their fish would already have died. The oxygen usage by the plants respiration is the final straw, but it is a very minor factor in the bigger picture.
At the end of the photoperiod your plants will have
- fully saturated the water with dissolved oxygen,
- they will have transported oxygen into the substrate via their roots (this is particularly true of emergent plants),
- they will have stored oxygen in their tissues.
- They will also have removed NH4+/NO2/NO3 directly from the water column and from the substrate (biological nitrification is an oxygen intensive process).
- Plants will provide a much larger area for microbial colonisation both on their leaves and, more importantly, in their rhizosphere in the substrate.
All of these factors mean that, even at night, planted aquariums usually have higher oxygen levels than un-planted aquariums.
If you think it really is a issue then you don't really need CO2 to make those nice tanks you see, it just takes more time.
I'm not a CO2 user, mainly because I can find quite enough ways to kill my fish without adding any extra ones. I like my plants to grow fairly slowly, so I run fairly nutrient poor, but even so I still have very heavily planted aquariums.
Have a look at Troi's tutorial <
"The soil substrate....."> for a way of getting more growth without CO2, and <"
Maxing CO2 in low tech...."> for some pictures and discussion of tank architecture.
cheers Darrel