Low O2 in plant tank? pH values

[DTs]

I have a feeling that my tank has low O2 and may need to run an airstone at night. What do you think? Suggestions?

Here's some data:

90g heavily planted tank
Pressurized CO2 w/controller (pH kept at 6.8)

I use 100% tapwater and do 50% weekly water changes:

Tap water pH = 7.4
Tap water pH after heavy aeration = 8.0

Tank water pH = 6.8
Tank water pH after heavy aeration = 8.1
dKH = 4
Temperature = 80 degrees

Lighting is 150w 6000k DE bulb, Giesemann Nova II with electronic ballast. Photoperiod is 8 hours per day.

[125gJoe]

Originally posted by DTs
I have a feeling that my tank has low O2 and may need to run an airstone at night. What do you think? Suggestions?... ... ... Running an airstone at night will not cause problems. You may want to run it for just a couple/4 hours at night, on a timer.

[djlen]

What is happening that is causing you to believe that you have low O2 content?

Len

[DTs]

I had bought 20 rummy nose tetras and lost about 9 of them over two weeks. Then, I lost 4 more when I dialed my pH down to 6.5.

I noticed when I do a water change the fish perk up. I do a 50% weekly change with heavy plant growth, so they're not perking up due to a decrease in pollutants. I know fish tend to perk up regardless, especially South Americans, when doing water changes.

Then, I thought to do the pH test before and after aeration, and thought the resulting values might possibly indicate something like low O2. So, I posted them here to see what you guys think.

So that's the long of it. Someone else e-mailed me privately and said my tank runs exactly like theirs and there's nothing to worry about. I'm just concerned because I put in a batch of Altums and I want them to have as ideal of conditions as possible.

[plantbrain]

What is your KH?
5-6 or so?

Anyway, Rummy's should be sat on till you see they are in good health before you buy, same for Altums and Cardinals.

Let the LFS lose, ask them to save them and that you'll buy them etc but want to see them eat etc.

If you have concerns about O2 at night, try getting the plants to produce lots of O2 during the day to make it through or consider moderate stocking levels also.
Another issue is having moderate surface movement, not too much, not too little.
Too much will drive off a lot of CO2, a little surface movement will also but...........CO2 is cheap and easy to add a little more if needed, fish? No, they are not cheap, so balance the surface movement.

Few folks use night time aeration, but there's nothing inherently wrong with it.

It will actually lower O2 levels if you grow the oplants correctly at least for most of the night.

There's only perhaps a 2-6 hour window where the O2 levels is ever below 100% staturation at night and it might drop to 90% with a moderately heavy fish load.

Also, turn the light on for 10-11 hrs.

Regards,
Tom Barr

[DTs]

Thanks Tom, I was hoping you'd give your .02.

I'm going to increase my photoperiod as you suggested. My plants give off tons of 02 during the photoperiod, so hopefully this will alleviate any 02 deficiency issues.

Believe me, I've tried asking the LFS how the rummy noses are doing, etc., and they always so "great", so that hasn't helped minimize losses. I'm down to 5 now and they look great.

Getting healthy altums is a nightmare. I think the only way to succeed is to find specimens that don't require shipping that have already been in the tank for a month, are healthy and eating well. I've spent a ton of money on having altums shipped to me only to receive the box with 62 degree water and dead fish. I actually have some that survived shipping; now I'm just waiting to see if the cold shipping screwed them up. They're eating worms, but not enthusiastically. It seems if they make it past 2 weeks, then I'm probably good to go.

[plantbrain]

I will not buy fish unless they have been there 3 weeks and eat also. No buts, and's ifs, "yea, they are great" baloney about it.

Regards,
Tom Barr