What deficiency is this?

[Larry Miller]

I've been fighting this for a while but am still struggling. I've added iron and that seems to help for a very short bit then the same thing happens again. Have added potassium via Kelp tea and banana peals in GB. Still no go. These plants are also growing slow, although my tomatoes seem to be doing just fine. Please Help?? 

My system is a 600 gallon system with tilapia, goldfish and bluegill. water temp is in the 80 deg. range, and fish all are growing well and seem happy. PH is in a neutral range right around 7. I use rain water to refill supplemented with de-chlorinated tap water when needed. I am in the San Antonio area. 

[George]

Not sure but I'd add a couple of tbs Epsom salt (magnesium)

[Larry Miller]

Thanks George. I have put epsom salt in before but it's been a while and I was just reading that many tanks need it on a regular schedule. 

George said:

Not sure but I'd add a couple of tbs Epsom salt (magnesium)

[George]

I add epsom when I add iron

good luck

[Alex Veidel]

Yeah, it's either magnesium or iron (or both). How much epsom salt did you add last time?

[Larry Miller]

I added around 3 Tbsp of epsom salt and probably 1.5 times that of Iron about 3 or 4 weeks ago. Just added 4 more Tbsp of epsom salt and about the same amount of Iron again yesterday. 

One thought I had is that I use a sand filter on occasion when my water starts looking bad, but when I start it It smells bad and you can tell that there is anaerobic action in the initial water exchange. I was reading that low Iron can be a sign of anaerobic areas in GB's, so could this be causing the problem with my system?

[Alex Veidel]

I think you may still need more magnesium in your system. Try dosing for around 15-30ppm magnesium.

Ppm is the same as mg/l. 600 gallons = 2,271.25 liters (let's round that to 2,300). So it takes 2,300mg of epsom salt added to 2,300 liters of water to get 1ppm of epsom salt. Epsom salt is 10% magnesium, so it takes 23,000mg, or 23g of epsom salt to dose 1ppm of magnesium. 23g x 15 = 345g. 345g = 12.17 oz.

So, in order to get 15ppm of magnesium, you'll need to add around 12.17 oz for a 600 gallon system.

[Larry Miller]

Thanks Alex. I will add some more epsom salt today and try to bring it up. I have already noticed some increased plant growth since I added some a couple of days ago, so I'm guessing this is the problem.