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Hi Everyone,


I live in Austin, TX, and my tank ranges from 74degrees in the morning to 91degrees in mid-afternoon. I don't see fish adapting well to this range at all. It is a glass tank that sits above ground, and it is in shade all day. I plan on putting some shade netting around the tank anyways, to hopefully cool it down a bit more, but I don't think it will make much difference. Does anyone have any suggestions?

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It looks like you only have about 100 gallons of media bed.  I would say that is perhaps appropriate for 14 fish to grow out to 1 lb each.

How much extra aeration do you have?

What is the water temperature on a hot afternoon?

What is your Ammonia, Nitrite, Nitrate and pH?  (saying they are "good" doesn't answer the question.)

If the "dead" fish seem to be really skinny or eaten by the other fish then perhaps part of the problem is they are really hungry and trying to eat each other.  Instead of goldfish flake, you might want to get some of the high protein Tetra flakes that are like 46% protein since the little tilapia have an extreme protein hunger.  Unfortunately, you are under filtered for the amount of fish you have and with the heat and if you are not running enough extra aeration, I would actually fear that low DO might be more of a problem than not getting enough to eat.

I have exactly 100 gal of media bed at this time and am poised to double that. My high stocking density is a combination of two factors. 1) i never seem to be able to produce enough nitrates(see below), 2) i am aiming for a 1 fish for every 3 gals of capacity. I haven't exapanded yet because 1) i am having problems getting my seeds to sprout(a topic for another thread), 2) my fish keep dying. Until i can overcome those two problems i find myself with residual grow bed space.

I have no extra aeration, while 90 is the highest fish count, i was able to sustain 60-70 without a problem just a couple of months ago. granted we had cooler temperatures then. DO is something i have considered, which is why i asked for a recommendation in my original post.

I have not been tracking my temperature. until recently it didn't seem to be an issue.

Ammonia, nitrite and nitrates are always 0, the only way i can ever get a reading above 0 is to supplement ammonia. At one point i was adding 1oz of ammonia 3 times a day, and never went above .5 ppm of ammonia. i did that until i had about 10-20 ppm of nitrates and then started cutting back until my nitrates were down around 5ppm. I like to keep a residual level of nitrates around to ensure my plants are getting all they want, without having too much as to negatively affect my fish. However, since i have been working out of town i have not been adding any ammonia and when i checked everything on thursday, all my indicators where again 0. Honestly, i usually don't check these more than once a week because they are hardly anything other than 0.

PH is 6.8/7.2 according to my API freshwater master test kit. I check my ph a couple of times a week. Since i have to add water fairly regularly, i keep a close eye on it. My city water here has a PH of around 8.5 and my rain water comes in under 6.0. so i use a combination of the two to keep my tanks full and to balance my PH, thus i have to monitor my PH to keep it in check. Even when i am only home for a couple of days, will add water as necessary and monitor the PH until i leave to ensure its not out of range. I try to keep in mid to high 6's.

depending on how long the dead fish remain in the tank, they will be "nibbled" on. I have found some that are completely intact to ones that are probably less than half eaten.

I am going to switch up my food today, the other thing would be the DO, and if you could recommend a way to monitor that i would greatly appreciate that.

thanks so much.

Most DO meters are going to cost at least a few hundred dollars.  I have never owned one.  There are a couple test kits out there you can use to test DO but the more reliable ones are a bit complex to use and come with a pair of gloves just to use the test kit chemicals.  I have only actually used it a few times.

Another indication of Lo DO would be if the fish are hanging about almost entirely at the surface (you might have to prop up the cover for a while so you can sneak up and peak without scaring them back down to see if they are hanging out in the higher DO region right at the surface.)

Now I've never actually reached a point in my systems where it was hot but I didn't have enough nutrients for the plants.  My problem usually seems to be the other way around in that it is hot, I have too much nutrients and not many plants seem to like to grow in the heat/humidity here.  But anyway, I have run into the problem that when there isn't enough aeration, dissolved oxygen or circulation the fish will quit eating.  My old backyard system originally didn't have any supplemental aeration and during the cooler months things were fine and the bluegill were eating well.  Then around May the bluegill went off their feed and didn't eat much anymore.  I tested the water and couldn't find anything wrong, so I went and got the backup air pump and set it up out there and added an air stone to the tank, the next day, the fish were eating well again.  This seemed to co-inside with about the time that the overnight water temperature quit dropping below 80 F.

Now I expect that your tilapia may not have gone off their feed but, before even considering adding a automatic fish feeder, I would definitely add some supplemental aeration since if anything goes wrong with the feeder and it over feeds, you want to make sure there is some extra insurance of good dissolved oxygen levels going in the tank to help you avoid a total fish kill.

When you do feed, How Much do you feed?  And how fast do they gobble it all up?

The fish do seem to hang out at the top of the water, whenever i lift the lid they begin swimming around in anticipation of being fed. I haven't really noticed them "not eating". every time i put food in the water they all begin swimming around eating it up. I have been using Tetra brand "Pond" fish food for Koi and goldfish, listed with 40% crude protein. I did pick up some Tetra brand cichlid "crisps" mighty expensive but at this point i just need to figure out whats going on. It is listed at 46% crude protein so at least that is covered.

I feed my fish twice a day, morning and evening. I have a 1oz scooper that i overfill and sprinkle over the surface of the tank. As soon as i open the lid the fish start swimming around and then they feed quite exuberantly once i put the food in the water. I've never timed how long it takes them to eat the food but if i come back several minutes later it is all gone. sometimes i see little pieces in the water that have started to sink and i will find a small amount in the sump tank but for the most part they are eating everything.

I just peeked in on the fish and the smaller gold fish were at the top hanging out and once i lifted the lid they all started moving around maybe 1/3 of the way down. I put in a thermometer so i can start tracking the temperature.

Get some supplemental aeration of some sort going on.  Either constant strong spray of water or an air pump with air stones or both or perhaps a venturi injecting bubbles down into the tank via a water pump if an air pump and air stones isn't easy.  Then you should be able to feed as much as they will eat in 15 minutes.  As in if you feed them and come back 5 minutes later and they have eaten it all, you can feed a bit more to the point where you figure about how much they are likely to eat in 15 minutes.  Then you can start to give them that much at first and check back 10 minutes later to see if you can give them even more.  Keep in mind as you start increasing feed this much you will have to do some extra water tests to make sure you don't get ahead of your bio-filtration.

I would not recommend doing this until you have some extra aeration.

AND once you have extra aeration and the fish are getting fed more you can wait and see if that makes a difference or see about adding a fish feeder.  DO NOT FEED AS MUCH using an automated feeder as you would when you are there to observe them.  Perhaps set it to only feed once per day and only part of the amount that you might give as a normal feeding.  OR you might even be able to use a cheap small aquarium feeder that might only feed a small amount of high protein flake or small meal or pellets but do it three times a day.  Problem is most feeders are a pain to clean and if they can feed too much to the fish at once, they probably will or you could mess up when setting the timer and wind up dumping the entire hopper when you set the off time to PM when it should have been AM or something as silly as that (YEP I'VE MADE THAT MISTAKE.)

Poised, I like it.  I installed one of these a couple of weeks ago - don't think I'll have further worry about DO.  Consumes 20 watts and puts out a lot.  Will probably use it to lift water at some point.

sticky said:

I have exactly 100 gal of media bed at this time and am poised to double that. 

If the water in the tank is really calm, I like to provide at least 1 CFM for each 400 gallons of fish tank water and of course kinda like water pumps air pumps also have pump curves though the are based on water depth not pumping height.  So a pump that produces .98 CFM and has a max depth of 7 feet, that means it really doesn't pump much if any air down that 7 feet.  So if you are pumping to the bottom of a 28" water depth of fish tank into an air stone, you want an air pump that will deliver at least the amount of air you want per minute at about 38" of water depth or about 1.3 psi.  28" is about 1 psi.  The Medium pore air stones I use count as about 10" of water depth.

Unfortunately the 123 ponds doesn't give a pump curve for that air pump so it is had to say how much air it delivers at different depths.

Thanks so much for the input.

after careful consideration i think i am going to buy a new water pump. the one i have is pretty much maxed out at present and i think it might even be slipping a little because i am having problems with my bell siphons kicking in which after some tinkering around a little, i have determined is from poor water flow.

So, if i upgrade my water pump, i can overcome my siphon problem, i will be ready to expand my grow beds and i will have enough residual pumping capacity left over to set up a water spray, as you suggested, in order to supplement my oxygenation.

It works out so perfectly, in my mind. Usually the first sign i should be worried .

I want to point out my own recent experience as a word of caution. Now I am dealing with an extremely big fish tank (swimming pool) and had little problems until one morning about 3 weeks ago. We have had some high temps here...close to 100 for weeks straight.

well, the combined effect of warm water not holding as much O2 as slightly cooler water and the effects of algae and phytoplankton consuming oxygen rather than producing it at night, all hit me hard early one morning. At about 6 in the morning, I had hundreds of catfish at the surface gasping for air. I had not seen this before or after.

I immediately pulled some lines to splash water directly back to the pool rather than go to the growbeds. I figured oxygen was a more immediate threat than filtration. Too little, too late.

I came home from work a few hours later with another fountain pump to just splash water up into the air. I pulled something like 65 dead fish at that time. a quick ammonia test showed it still 0.
But I knew that would change soon.

By late afternoon, I had lost over 250 catfish. Skin was starting to slough by that time and it shot the ammonia up for a short time.

Just realize when you hit the wall of low o2, the results are sudden an unforgiving.


I think you nailed it.  I had posted a response (from my email) asking about DO before I read the thread.  Once I saw folks were all over it, I deleted my response.  I pump a bunch of bubbles into my fish tank.  Not only from agitating water but from an aid pump as well.  It get hots in Beaumont as you know but I have been able to keep fish alive that were not suppose to live in temps anyway close to what I was getting.  I can only credit to the massive amount of air I am putting in the water.

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