FishProfiles.com Message Forums

I have a 43.5G heavily planted tank with pressurised C02. I have tested the water parameters as follows:-

Ammonia: 0
Nitrite: 0
Nitrate: 20
pH: 6.7

A water change would not alter the nitrate, as I have that amount at least in my tap water. The tank has been set up since January 2006 and I do 50% weekly water changes.

In this tank are:-

5 otos (although I can only actually count 3, but I can see no dead otos anywhere)
1 M & 1 F guppy
10 harlequin rasboras
2 rainbow fish
3 platys
a couple of free swimming platy or guppy fry
2 sterbais

My platys have started dying on me.

No harlequins have died, but don't think they are as actively swimming around as a little while ago. The guppies, rainbows & remaining platys seems as active as usual.

The only thing I can think of (as the water is testing ok) is that maybe the pH swing is too high from when I have C02 to when I don't. I'm going to slow the C02 rate, so that pH doesn't drop below pH 6.9 and tomorrow, just before it switches on, I'll see how high pH gets.

Can anyone think of anything else, besides my pH that could be causing the deaths.

Any suggestions would be greatly appreciated.

Cheers
TW

Both your guppies and platies prefer a hard water, alkaline environment. Since few guppies and platies are caught from the wild stocks and exported to the trade, the species have become much more flexible as to their living conditions.

You didn't mention how long that you have had the platies although you did mention when the tank was set-up nor did you mention GH, KH or temperature. Generally the fish does well with pH from 7.0 to 8.3 and temperatures from 68F to 79F (20C to 26C).

In contrast, your rasboras prefer a pH from 5 to 7 with temperatures of 73F to 82F with soft to medium water hardness. Similar comments may be made for the sterbais and otos. However, your rainbow fish prefer medium to hard water...



__________
"To steal ideas from one person is plagiarism; to steal from many is research."
researched from Steven Wright

Hi Bob

Temperature is 26degrees. KH is 5 and I don't have a GH test kit. I have had the platys since the tank was set up - they were my cycling fish. They were mature fish & the females have had several batches of fry since they've been in the tank.

Thanks for the info about what my different fish like.

I have just discovered that my solenoid valve doesn't seem to be shutting off the C02 when lights are out. I don't know if that is the problem, however, I remember lots of members from the planted forum telling me that they run their C02 24/7 and don't run into problems with their fish, so probably not.



Cheers
TW

If I remember back a few years a local LFS had massive deaths overnight the cause was that some thing went wrong with the Co2 and too much was injected into the tanks. They managed to save many by doing massive water changes.

Yes fish do prefer diferent water peramiters but because of the breeding in capitivity they seem to "survive" in community tanks. That does not mean all community fish are happy in same tank there is a big difference between survival and a totally perfect set up tank for one species or a group of species that prefer exactly the same conditions.

Have a look in [link=My Profile] http://www.fishprofiles.com/forums/member.aspx?id=1935[/link] for my tank info

Look here for my
Betta 11Gal Desktop & Placidity 5ft Community Tank Photos

Keith

Near enough is not good enough, therefore good enough is not near enough, and only your best will do.
I VOTE DO YOU if not WHY NOT?
VOTE NOW VOTE NOW

Thanks for the advice all. I now think it was the difference in the pH between CO2 on and CO2 off. When off, my pH could get as high as 7.8 and with it on, was getting as low as 6.7. I think now that I've corrected that big swing, all seems better in the tank.

Do you think this might have been the problem?

Cheers
TW

Big changes in a short time will stress out the fish and can make them sick. Always try to keep the levels in the tank as stable as possible to prevent stress and illness. If you have to make a large change try to do it slowly so the fish can adapt to it. A big pH change like you are having can play a big role in problems as I will bet that the pH is not the only thing changing.

It is like you going from a 90d f room to a room that is only 30d F. It is a huge shock to your system and can even make you sick. If you do it slowly though your body will adapt and be fine with the difference.

---

Live life to it's fullest
Who knows what tomorrow holds

---

Absolutely! Until I read your last post, I was going to ask you to measure your pH in the afternoon and then first thing in the morning to see the pH swing.



__________
"To steal ideas from one person is plagiarism; to steal from many is research."
researched from Steven Wright

Yep, it's what I suspected myself. To stop the swings, C02 is runnig 24/7, but with an air stone going on during the lights out period. All seem much better since I made this change.

Thanks for the advice.

Cheers
TW