Questions regarding kh...ph..co2 and overflow filter

[roghib]

Sorry for redundant or silly questions which will probably seem common sense to most of you. Have read various posts and web sites but still find myself sorely lacking in understanding.

I have a 90g planted tank with an AGA Megaflow overflow system with sump.
I set up my tank a couple months ago and after a fishless cycle I placed fish in the tank about 4 weeks ago.

My fish are starting to die at an alarming rate and now thinking this may be ph related stress.

My kh has varied a little over the past month ...Tap kh is around 8-9 Ph around 8.

I do a 50% water change a week. Until today I hadnt monitored tap kh.

My tank has seen a kh of around 3 a few weeks ago to around 6 ish now. I have been injecting co2 (currently around 3 bubbles per sec). My ph is between 7.2 and 8 depending on lighted or unlighted time (Obviously very bad). My co2 injections shuts off with lights.

1.) Can KH change throughout a week or is this a pretty much a constant with water placed in tank? b: and if so how?

2.) Using the calculators I have gotten close to being "in the green" but have yet to achieve this. Is this about impossible using an overflow filter config like I have? My dream is a heavily planted fish/plant tank. Unfortunately tank was hugely expensive and now stuck with what I have. Note: I have reduced all turbulance of water re-injected into tank but cant stop turbulance and bubbles in overflow chamber.

3.) Should I stop shutting my co2 off at night with lights or will this quickly co2 poison fish?
b.) If I should be shutting it off, should I get automated ph controller? Worried I am gassing off at night and my ph rises and the change is creating stress. I am at a loss as to how to stabilize the kh and ph in my tank short of doing away with the co2 completely.

I am lost....at the expense of my fish.

[fresh_newby]

IMO pH doesn't fluctuate enough at night to cause this. I have always had my CO2 shut off an hour before lights go off, and turn on an hour before lights are on in the morning. My pH doesn't fluctuate that much to cause stress. As for CO2 "poisoning" if you have a normal 3bps in or around....you are not poisoning your fish. Do you see them gasping at the surface regularly? If so, perhaps you need more water movement to facilitate gas exchange and get some O2 into the water column. I have a pH controller, but I have to say, my bubble rate is steady and with the CO2 turning off at night, I do not need one. It was one of my impulse purchases.

I had a period of fish dying off and later found out it was a parasite outbreak. <yes I dissected one of them afterwards> There are many reasons for fish die off, and a lit of time it is a domino affect...a few die then more.....it doesn't sound like you are "poisoning" them with CO2 to me...not do I think the pH change over night is casuing any problems. I would look into other reasons....and observe their behavior.

[Rex Grigg]

pH changes caused by CO2 do not harm fish. This is because in normal water pH changes are caused by changes in the kH and TDS. This can cause osmotic imbalance in the fish. With pH changes caused by CO2 there are no changes in the kH or TDS.

Normally kH doesn't change. But there are some things that can cause kH to drop. Driftwood, peat based substrates, excess peat in the substrate are a few.

Look into getting a Durso standpipe for the overflow. http://www.dursostandpipes.com/

Sorry you made the mistake of doing a fishless cycle. There is NO reason to go though that with a planted tank.

Have you by chance tested for ammonia and nitrite?

[roghib]

Ok guys thank you for input.

Yes, I have checked ammonia and nitrite at least twice a week and never do they even show a trace. At this time I do not suspect co2 poisoning...more was along the lines of ph shock. Was only concerned about the co2 if I left it on at night.

I am grasping at straws as to the deaths as I can see no bad water conditions nor sign of distress much before they die. I did buy all the fish at one time and introduced them together. Perhaps I am just back to one being sick and has passed this on.

I had jumped on the ph thing when someone had me check tank parameters during lights out and I noticed a ph change.

I guess we will continue on and look into new pipe so I can continue to pursue the coveted "green" zone.

[fresh_newby]

Ok guys thank you for input.

Yes, I have checked ammonia and nitrite at least twice a week and never do they even show a trace. At this time I do not suspect co2 poisoning...more was along the lines of ph shock. Was only concerned about the co2 if I left it on at night.

I am grasping at straws as to the deaths as I can see no bad water conditions nor sign of distress much before they die. I did buy all the fish at one time and introduced them together. Perhaps I am just back to one being sick and has passed this on.

I had jumped on the ph thing when someone had me check tank parameters during lights out and I noticed a ph change.

I guess we will continue on and look into new pipe so I can continue to pursue the coveted "green" zone.

It is definitely not pH fluctuation. Perhpas it has something to do with adding your fish all at once. <by the way you should always cycle a planted tank with fish> but gradually.