Weird fish behavior

[Cossack1977]

Ive moved into my new place and been here for about 3 months. During the move which i had to do in 2 stages i moved all my fish from my 6ft tank and put them in a temp 4 foot tank for about 2 weeks. the tank was running 2 eheim 2128 and a trickle filter. the fish were there for a bout 2 weeks without a problem.

Finaly moved into new place and set the 6ft back up. washed the gravel for like hrs and other then having 50% less plants(they died) eveything was identical to how its been for over 1yr.

tank was up and running for about a week no probs and then.

during the day all fish were fine. a few hrs after dark all fish were at top of tank gasping. lets just say within a few days i lost about 30 fish.

i tested all paramaters first time in like a year and they were perfect 0 to ammonia, nitirite temp 26degrees, ph 7.

ended up setting up 2 power heads to really break the water surface and all seemed fine after that. left the power heads running for about 1 week then took them off. all fish were fine for about a month now its happening again.

2-3 hours after lights go of all fish go to top of tank

help!

 

[Saz]

That sounds really strange. Have you tested the oxygen concentration? You may want to consider staging the turning off of the lights so it gently gets darker so not to cause any stress to your fish. Other than that I really don't kow. Is there anything else you turn off at night apart from the lights, possibly accidently?

 

[Cossack1977]

the only thing i can think off is that there is about 50% less plants at moments so maybe not enough oxygen going into tank during the day.

yes i have a high fish load and i used to have a high plant load to go hand in hand with that. maybe that is the cause.

i dont even have my co2 running yet

since moving into the new place i havnt really done anything different when turning the lights off.

 

[Dubby]

Seems strange..... it appears almost as if the oxygen levels are dependant on the light, which cant be true !!! What are the nitrate levels?

I would look for other reasons for the deaths. Can you not position the outlet of your filter so that it disturbs the water?

 

[Cossack1977]

Seems strange..... it appears almost as if the oxygen levels are dependant on the light, which cant be true !!! What are the nitrate levels?

I would look for other reasons for the deaths. Can you not position the outlet of your filter so that it disturbs the water?

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ive got it disturbing the water at moment but yeah its as if the lights or causing an oxygen problem

but putting in a ton of plants over this week and kicking the co2 back in so i dont want any water disturbance. but im a bit worried about the fish

 

[Dubby]

Its probably something else in the water that wasnt there in your old place. Does your dechlorinator get rid of heavy metals and chloramines?

 

[Jules H-T]

Does your dechlorinator get rid of heavy metals and chloramines?

Good idea. Also consider the possibility that it might be the other way round (used to be in a heavily chorinated or chloraminated area and now are not, so your conditioner is now adding too many chemicals to the water and you need to add less)?

Is the temperature fluctuating wildly at any point (although you'd expect it to be hotter in the day so the logic doesn't really work)? Perhaps because the ambient temp is 27 in the day the heater is off, then when it drops to 24 in the early evening, the dodgy heater kicks in, but doesn't cut out until 30?

 

[rdd1952]

The high fish load and less plants could be the problem. The fish are creating more CO2 which the plants easliy process during the day but once the lights go off and photosynthesis stops (or severly slows) they can't handle all of it so the CO2 level goes up and the oxygen goes down. Would probably be worth staying up one night after the lights go out to test the pH and CO2 when they start having problems. With the large fish loss, are they still doing that? If not, maybe the loss of fish has cut down on the amount of CO2 they create and lessened the problem.

 

[Angry_Platy]

it appears almost as if the oxygen levels are dependant on the light, which cant be true !!

It can be true and it is. During the day plants use the energy from the light to transform CO2 into food...which basically means the plants grow. During this phase they are also producing oxygen=very happy fish.

At night time when lights go out the plants start taking up oxygen from the water...in nature this is almost like a balance thing where the plants will keep the oxygen level almost constant from day to day.....same as in our tanks. If you have removed some plants then less oxygen is being produced during the day. Perhaps you might want to consider shortening your lighting time and giving them more dark.

 

[Cossack1977]

thanks guys some good ideas.

yeah i think its because of the plant fish ratio.

As one of my good friends owns an awesome aquarium i never went by any fish stocking rules the only rule i adheard to was that every 3 fish i bought i bought a plant to go with them. so before i moved a had about 120 fish and over 40 plants so alot of oxygen being produced.

now im down to about 80 fish fish only 10 plants.

tap water is pretty much same here as my last place.

i add exactley same chemicals and amounts as i always did and same brand products.

lights go on and off at same times.

ive tested the ph and temp during the day and night with no real difference. tank drops 1 degree @ night

 

[rdd1952]

I strongly think it is the lack of oxygen at night because of the hig fish load and lack of plants. Adding an airstone would be the quickest way to solve that problem.