I have been battling very poor plant growth over the summer months to date with all plants except the trusty spinach failing to yield much edible produce. I have spinach, lettuce, spring onions, tomatoes, chillies, capsicums and strawberries growing at present and I gave up on all varieties of squash and cucumbers as they repeatedly died after a week in the grow beds. I have concluded that water temperature is the problem with my system frequently reaching and holding 29 degrees, with the odd drop back down to 18-19 when there is a cool change. The cool changes seem to bring about a brief improvement in plant health - evident only in the color of the leaves becoming greener.
My 248 Silver Perch are doing well with no losses in recent months and only a 3.2% loss overall since I got them in April 09. Water conditions are as follows;
PH 6.4 on average (varies between 6.4 and 6.6) buffered by crushed sea shell
Ammonia 0.25 (consistent)
Nitrates varying between 0 and 5 (more so hard to distinguish from 0)
The Digger guide to earth based gardening suggest that a very warm soil is 18 degrees and therefore I am left wondering whether the plant roots are not coping well.
I augment the nutrients every six months with mineral fertilizer purchased from Murray and there is no evidence of any iron deficiencies. Interestingly my winter growth was very agressive with water temperatures maintained at 18-22 degrees through heating (won't be heating this years as it was too expensive).
If it is water temperature, given my location of Deniliquin in NSW I would expect that Victorian and South Australia aquaponicists (is there a word for the aquaponics enthusiast) would be experience similar poor growth rates?
Any thoughts and opinions are most welcome and appreciated.