Minnow tank problems

I got a 200 gallon stainless tank with insulation on all sides and bottom. Got a pond filter in take with roughly a 600 gph flow. I have filter media around intake of pump and pump feeds into a 5 gallon bucket of bioballs. Needless to say minnows have been dieing to quick. Losing 1-2 dozen a day. Tank had been up for maybe 2 months minnows in maybe 3-4 weeks now. I've been changing 100 gallons of water every 2-4 days and feeding them every 3-4 days. I had 2lbs to start which ik is a lot for new tank but expected the lose of them so wanted more to start. Water temp round 64-70 degrees and using rain water from my neighbors cistern. I've been testing ammonia and it's off the charts even after the water changes. I don't know what to do. I'm about ready to give up but my local bait shop has been out 3 different times this year. Any suggestions.

I'm gonna guess you are feeding them too much.

They eat it all within a couple minutes. I was wondering if I could be getting ammonia from my neighbors cistern

Try getting the temp down to 56-60. That is where I try to keep mine. And I keep 2-3 pounds in 40 gallons of water and only change 20 gallons at a time every 3-4 days

Are you adding salt ?

Feed them very little bout once a week. Feeding them way to often. They won't starve. After you feed them in about 4-6 hr's change out about half the water. You also need some charcoal in your filter system.

I do have a charcoal with my filter pad and yes I add salt the other day with a water change but no I haven't been adding salt every time. I prolly just need to wait for the tank to cycle but it feels like I'm messing something up

What I have not heard you say is your aeration supply. Is there alot of foam on the side of the tank? Is the tank in the shade? Talk to me about your aeration. If you go to Walmart and purchase an aerator designed for 60 gallons that will supply sufficient air for 2 pounds of minnows. 10 chances out of 9 your problem is ammonia from the cistern. The water is probably slightly septic. Do you have well water or city water? Answer these questions then we will go to the next step.

Sorry I forgot to mention that stuff. Yes tank is in constant shade never sees the sun. It's in my carport. And yes I have an air pump. Elemental O2 Commercial Air Pump, 951 GPH | Allied Aqua with 6 stones. 4-1" and 2-4". Plus my bucket of bioballs is prolly 1.5-2' above tank And I'm on city water and I do treat it if I have to use it. But since my neighbor doesn't use his cistern it was free water. I am gonna test his water tomorrow to see if im introducing anything I shouldn't be. And I started putting frozen milk jugs in it to try to cool water more until I prolly buy a chiller. Tomorrow night I am going to go get a complete water testing kit and new charcoal pads so I'll know more about water then.

You have sufficient air if not too much air which can cause excessive turbulence. I do not see a need yet for the frozen milk jugs. I suspect the culprit is the cistern water. Depending on scfm of air being supplied by the stones I may suggest you remove the 4" stones because too much turbulence will stress them. What type of minnows are in the tank? Let's focus on the water test results.

They are shiners and I actually thought about removing the 4 small ones cause they float up to the surface. The 4" stay at bottom. I'll remove the stones and get the water testing information tomorrow night or Saturday

If you are going to use the 4 small ones then zip tie a sinker on each to get them to the bottom. They provide little value floating on top of the water. The 4" stones are allowing the air to rise from the deep water and the oxygen to transfer into the water. Shiners are fish that do better without alot of turbulence. One 4" stone may be sufficient for the minnows.

I have bee told you could use city/ county water IF you store it a few days in a drum or container with no lid,said the chlorine will evaporate .I don't know this for sure though.Has anyone done this?

Yes that will work but I got additive to remove it.

From my experience working on a fish farm a constant temperature in your minnow tank will help you greatly. We have flow through setups where water right out the well runs through the tank and flushes to the ditch usually maintaining a constant temperature. The ammonia usually spikes from the fish dying so keeping the minnows constantly picked is a necessity. Also I've never had much luck holding shiners for more than a couple weeks. Usually the fish we sell have only a two-week shelf life from the pond before you start dealing with die off. Shiners are also much more difficult because they are more sensitive than Fatheads.

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I have been keeping both crappie and 4-6 inch shiners in my basement all year for stripers and crappie. I built my tank out of a 275 gallon tote. I started out with 6 lbs total minnows and have been using them all winter. I am down to probably 15 or 20 large ones left. I only feed maybe once a week or sometimes less and do a few small water changes a week when I had them all in. Now I hardly do any water changes. They require much less food than you would think. Temp is the key as well. Mine stays in the low 60's. At the beginning I would lose 5-6 minnows every week, but once I used maybe half, the looses were very small. Lucky that I have very good spring water to use.